Bullies can dish it out, but they just can't take it. This is an ancient boxing rule of thumb: a seeming psychological paradox that really is a straightforward truth.

Sugar Ray Leonard proved the verity of this maxim again tonight as he humiliated Roberto Duran with flashing combinations, glorious boxing skills and audacious courage.

For almost eight rounds, Leonard made a fool of Manos de Piedra, taunting him, beating him to the punch, disdaining him, laughing in his face, then smashing him with lighting blows from both hands.

Finally, with 16 seconds left in the eighth round, Duran could not take it anymore. His face, although a bit puffy, was unmarked. He had not been knocked down or even severely hurt. But, far more important than that, his Panamanian macho had been slain. The man who had been feared more than any brawler of his era, the man who had been both lightweight and welterweight championship and brought a 72-1 record into this fight, had been treated as though he were a pathetic little boy in a rage who needed to be cuffed about the head.

So, at 2:44 of that eighth round, Duran did what no one in the entire world of prize fighting ever dreamed him capable of doing: he quit. Later, he said he was retiring from the ring.

"I had no idea what happened," said referee Octavio Meyran. "I said to Duran, 'What happened. Go in (and fight).' He said, 'No. . .no more.'"

The Louisiana State Athletic Commission, presumably displeased with the manner in which this fight ended decided to hold up Duran's purse ( a reported $10 million) until he could undergo a complete medical examination.

Truly, Duran had enough tonight.

"I will never fight again," Duran said, after losing the WBC welterweight championship that he had taken from Leonard just five months and five days ago in Montreal.

"I got cramps in the fifth round in my right arm and side. They got worse and worse," said Duran. "I was weakening."

The lion had quit with a thorn in his paw. The man they said could be stopped only with an elephant gun had thrown in the towel because a faster, younger and smarter man was giving him a boxing lesson and mocked him in the process.

Typically, Duran was brutish to the end. "I feel I am a thousand times a better man than Leonard," said Duran after the fight. "Just because he beat me once doesn't mean I have to respect him. . .I am going home and count money."

Anyone searching for the cause of Duran's cramps can consider this. They may well have come from the bile when a bully's heart burst.

Leonard, who depended on a complete change of tactics to regain his crown -- and prove himself to be a fighter for the ages in the process -- was ecstatic, but gracious in his greatest moment.

"I beat Duran more mentally than physically," said Leonard, accurately. "The things I did, especially in the seventh round, demoralized him. But don't knock Duran.He will always be a great champion."

Told that Duran had made light of him, Leonard said quietly, "That's just Duran's nature. He wouldn't say anything else. I still respect the man."

Asked repeatedly about the shocking moment in the eighth when Duran simply backed away, turned his back, and waved a glove dismissively at Leonard as he quit, Leonard showed the spark of genuine feeling. "Maybe Duran had heartburn," said Leonard, critically. "Don't talk about Duran quitting. Talk about how badly I beat him. Duran's back, Duran's cramps. . .It's going to take a lot for people to accept that I beat the Macho Man, the Hands of Stone, a legend.

"It's simple. In the first fight (a unanimous 15-round decision) I learned Duran. I could change. He Couldn't."

None of the roughly 40,000 in the Superdome for this Super Fight could doubt Leonard's word. By thoroughly licking the 29-year-old Duran while he was still in his prime, Leonard established himself as a great champion in his own right. And, certainly, one of the most versatile champions in history, at the least.

Every trap was laid for Duran here tonight.The American crowd booed his introduction as much as the Canadian crowd had cheered him. Who should sing "America the Beautiful," but Ray Charles, the blues singer for whom Sugar Ray Charles Leonard was named. Even Leonard's costume was a surprise. Both fighters claimed to want to wear white trunks, with Duran, as champ, getting his way. However, instead of wearing red, as he said he would, Leonard entered the ring all in black (with gold trim) right down to his black socks.

Duran's surprises started immediately. In Montreal, Leonard had proved his courage, his ability to take Duran's best punch. So, tonight, he didn't need to. In Montreal, Leonard started fearfully, losing the first four rounds as Duran swarmed him. Tonight, Leonard danced the whole first round, letting Duran stalk and stalk, then, when he finally struck, nailing the Panamanian with a vicious left hook.

Seldom has any fighter done a more splendid job of going to school between one fight and another. Leonard measured Duran from long range and by the fourth round was stinging him several times a round with clean snakelike hooks to the forehead. When Duran bored inside, Leonard snapped his head back time and again with the uppercuts that he neglected until the late rounds in Montreal.

Most impressive of all, Leonard turned all Duran's stalking and bulling tactics against him. Once, Duran used every ring-cutting technique, got Leonard seemingly pinned and leaped in with a left hook. But Leonard with a shimmy of his hips like a football halfback, ruined Duran's timing, sidestepped him, and popped him in the temple with the jab as he danced away laughing.

Once, Duran lunged so desperately that he went through the middle of the ropes and almost fell out of the ring. The only embarassing moment all night for Leonard was when Duran once tackled him like a linebacker and knocked him on the seat of his pants with a push.

For Duran, the psychological Waterloo came in the seventh round. "I don't know why," said a grinning Leonard, "I just figured it was showtime."

Leonard stuck out his chin, inches from Duran's gloves, as Ali once had done to Liston, and when Duran lunged, Leonard retracted the chin and extended the gloves, smashing Duran in the mouth with a combination. Leonard did this not once, but repeatedly, dancing all around Duran, tempting him, then punishing him. Once, Leonard faked a straight right, then swatted Duran with a left hook.

The crowd was in an ecstasy of laughter and cheers as Leonard landed significant, if not crushing, blows throughout the round. "Just keep up the pace, and he's dead," yelled Dundee between rounds. The Sugar Man, however, knew even more. "I watched his eyes between rounds," said Leonard, "and they changed. He tried to sneer and leer.But I knew the truth. What punch paralyzed him? All of 'em."

Just as Liston stayed on his stool for an eighth-round TKO, so Duran's worst moment as a fighter will go into the books the same way -- TKO in the eighth. For the record, his cramps, if they existed, did not appear to damage his ability to fight. His face showed no pain. Between rounds, he did not dramatically favor his side. Certainly, he was in nothing like the pain that Ali, for instance, endured when he fought the last 13 rounds of a 15-round defeat with a broken jaw against Kenny Norton.

Boxing has a long history of champions fighting gamely until the end, even if they have injuries far more severe than cramps, which, at worst, can go away after a couple of rounds. Duran, however, was in no mood to go from bad to worse. His stamina was dwindling, while Leonard was as fresh as in the early rounds. On the three judges' cards, Leonard was ahead, 4-2-1, 4-2-1 and 4-3 -- margins which probably should have been even greater since only in the third round did Duran seem to score better. Duran knew that the first eight rounds were just prologue; worse awaited him and he ducked it.

"I have been fighting a long time," said Duran through his translator."I have gotten tired of it. I want to retire."

Are you embarrassed, he was asked?

"No, why should I be? This happens to everybody."

For Leonard, just 24, a long reign may be ahead. Certainly, his confidence should take a quantum leap forward after this night. In Montreal, he seemed dazed and almost lost as he entered the ring. Tonight, Leonard was so together, so relaxed, so confident, that he was loose and smiling during the introductions. He was so delighted by Ray Charles singing, and the hug and kiss that the blind musician gave him just before the first bell, that he almost seemed euphoric.With each round, Leonard seemed more delighted with himself as those long hours of gym lessons were paying off in trumps.

On Basin Street here, in the St. Louis cemetary, the names of many Lou'siana men are on the aboveground tombs. The epitaph on many reads: "Killed in a duel."

That is the epitaph for Duran tonight. This evening, Sugar Ray Leonard had the feet of a Bourbon Street tap-dancer, the blended combinations of a fine Dixieland jazz band and the punch of Ramos gin fizz.

It only took Roberto Duran to see enough of this demoralizing mixture.

For the rest of the boxing world, which has years more of the developing saga of the Sugar Man ahead of it, this night was just the delicious first course in the long championship feast of Sugar Ray Leonard's career.