Good on you for finishing the game, mate! It's definitely a tough one and a slog at that, but so worth it. Love this game.
Originally posted by: Grumble,Grumble
Hell yeah! Beating this game with Alucard was the easiest for me since you can transform into the bat, while Sypha's route was the toughest. Grant is somewhere in the middle, but he's my favorite by far. I've never done a Trevor only run through...Fighting the Doppelganger boss would be hard, since you can't morph between characters to delay the boss as a strategy.
The Doppelganger is definitely the worst boss in the game and the one that took me forever to beat the first time, but to beat him with just Trevor you'll want the holy water. There's only ONE holy water pickup in that whole stage, and it's during the falling castle section. It's in a candle on the far right side of the screen that you have to jump up and over quickly to go get. But it's simply the most effective way of dealing with him if you're using Trevor. I'm sure that's why they made it so tough to get.