The militia commander of the Phalangist Party, Bashir Gemayel, 29, has emerged as the most powerful figure among Lebanon's right-wing Christians after two days of fierce factional fighting that left at least 65 persons dead and as many as 200 wounded.

In a decisive, carefully planned strike, Phalangist militiamen overran positions of the rival National Liberal Party in Christian East Beirut the rugged hills northeast of the capital and 5 miles northward along the coast.

The National Liberals left their barricades and handed over their weapons, leaving their headquarters in those areas in control of the Phalangists.

Dany Chamoun, 40, the National Liberals' military commander, announced that he was resigning from political strife after Phalangist raids on his two residences, and left with his wife and daughter for a mountain retreat. h

Charmoun's father, former president Camille Chamoun, and Phalangist Party founder Pierre Gemayel, Bashir Gemayel's father, have met and made public pledges of unity in the last two days, calling for the regular Lebanese Army to patrol Christian areas.

The hard-line followers of Bashir Gemayel, however, have said they would accept the Army only if it entered Palestinian commando camps and areas under the control of the Syrian-dominated Arab league deterrent force.

No armed militiamen were seen through most of East Beirut. Phalangist sources said that part of the cease-fire agreement was that there no longer would be any gunmen or militiamen on the streets.

Nevertheless, the apparent hegemony of Gemayal's hard-line Phalangist worries Moslem groups in Beirut's western sector, Moslems were reported to be on alert following definitive reports of the Phalangist victory.

A Western diplomat commented that the Phalangists won because they were better trained and a more cohesive force than the National Liberals.

"In a country of absolute lawlessness, of course the fittest will survive," he said.

After a period of protracted war, it is natural that the younger generation will fight it out among themselves to reach the top, the diplomat said. As long as the elder Chamoun and Gemayel are alive, the Christian camp may be kept together.

"But what will happen later is anybody's guess," the diplomat said. The supremacy of the militant line of the Phalangists may spur like-minded militants on the Moslem-leftist side of Lebanese politics to try to gain the upper hand.

Many Lebanese fear that this could lead to an all-out confrontation between the Lebanese leftists and Moslems, Syrians and Palestinians on one side and the Christians on the other, in a repeat of the 1976-77 civil war.

A spokesman for the Phalangists said July 7 -- the first day of the latest round of factional fighting -- would be seen as a historical turning point in Lebanese politics, and called Phalangist offensive the first major step toward unification of the Christian forces and creation of a "national home guard and police."

"It's the first time that the Christians in this part of the world will be unified militarily in 14 centuries," the spokesman said.

He said, "The aim of the Lebanese forces and the mission of this national guard will be to liberate all territories within Lebanon's known international borders."

To the Phalangists, areas now held by Arab peacekeeping forces of Palestinians must be "liberated."

Although it was unclear whether the attempts to unify the Christian militants could be successful given the bad blood between various factions, the spokesman said the Phalangists would disband their militia at the end of the month with the formation of the national guard, which he said will include the National Liberals, the Phalangists, the Tanzim, the Guardian of the Cedars and the Assyrian-Lebanese League, which represents a Christian sect of at least 100,000.

Meanwhile, in a newspaper interview published today, Dany Chamoun referred to Bashir Gemayel as a "ruthless, cold-blooded murderer."

He told the newspaper An Nahar that his supporters in one coastal town were "annihilated, and then buried in mass graves without allowing their families to see the bodies or conduct proper burial."