Janeway, hands down.
For all the reasons given above, though I want to expand on a couple things:
1) She constantly exposed her ship to danger through mismanagement of tactical situations. I don't care if you're a scientist or the captain of a garbage scow assigned to Ruh'ra Pente- you don't wait until your shields are mostly gone to start shooting back. If your enemy has already started hurling subatomic death at you, descression has ceased to be the better part of valor.
2) You don't beat up on your officers for making human mistakes, and then go and do the SAME FRELLING THING a week or two later without apologising to said crewmember, even if you are the captain. More-over she did this constantly throughout the series.
3) in such a situation as being trapped 75 years away from home, you don't go and lock yourself atop an ivory tower and do a vulcan imitation that would drive Tuvok into instant Pon Far. you be a leader by example, and SOCIALIZE WITH YOUR CREW!!!!!!!!! Alienating your crew leads to lower moral, and worse. encourage second guessing and (at its most extreme), mutany.
It's established canon (such as canon counts with Voyager) that Voyager was her first command, and after seeing what she did with that command, it's not surprising that they promoted her to admiral. What, you ask? Promote her? why in the frelling hell would you promote such a horrid officer, you ask?
Well, it's very simple, really: A) She technically came back a hero, and B) promoting her puts her behind a desk, instead of in the Big Chair of a Starship. Busting her back down would have put her in a position to command a starship again, which as we've seen is a colosal no-no. Promoting her really WAS the best thing to do, as strange as it sounds.
I don't care if you're a scientist or the captain of a garbage scow assigned to Ruh'ra Pente- you don't wait until your shields are mostly gone to start shooting back. If your enemy has already started hurling subatomic death at you, descression has ceased to be the better part of valor!