1. "Power" is relative. Maranzano was the only one on your list who ever held the title of capo di tutti capi, but he held it for just a few months before he was murdered on Charlie Luciano's orders. I'd count Luciano as the most powerful because, after he got rid of "moustache Petes" Maranzano (and Masseria before him), he formed the Commission and made the Mafia a national organization. Even though he never claimed a super-title, Luciano was acknowledged as the most powerful Mafia guy in America. He continued to run his family even when he was sent away to prison. To me, that's power. Carlo Gambino ran the biggest family with the largest revenue in his time, but he didn't quite have Luciano's nationwide clout.
2. I don't know what you mean by "intense." The Bananna War probably generated more corpses than all of them combined. But the Castellemmarese War was more momentous, because it was the last gasp of the Moustache Petes, and led to the formation of the Commission and the new Mafia.
3. Joe Columbo supposedly was whacked on Carlo Gambino's orders because his "Italian-American Civil Rights League" and his TV appearances were way too high-profile for the Mafia.
4. If by "Vito" you mean Vito Genovese, he was essentially powerless after Joe Valachi's testimony. Probably the last hit he ordered was of Tony (Bender) Strollo in 1962, but Strollo was an underboss in his own family. Tommy Eboli ran the Genovese family for Vito while Vito was in prison, and took over when Vito died in '69. As far as I know, he had no hand in the Bananna War and the Gallo-Profaci War, the big events of the Sixties.