Truthfully, for me, the biggest thing I have issue with is Gabriel's remorse. Literally every "evil" thing he does before becoming a vampire - including becoming a vampire - is because he is made to do so by external forces or because there are no other options. It's kind of like Angel on Buffy the Vampire Slayer. I love the show and character, but Liam (the human soul of Angel) should not feel remorse for the actions of the demon who set up shop in his body when his soul vacated.
I can understand his remorse. It's easy to play the game and say "Well Gabriel, it wasn't your fault, Zobek made you do it" but if I take a second to put myself in Gabriel's shoes, it becomes less simple.
If I woke up one day and my wife was dead, I'd be heartbroken, devastated, and furious. I'd want answers. I'd want revenge. I'd have so much grief, anguish, and hatred, and I'd want to direct it all at someone. Now I personally have a daughter, which would give me a really good reason not to fall off the deep end, but Gabriel doesn't have that. When Marie dies, he has essentially lost everything. So Gabriel takes all of his hate and his rage and he goes on a monster killing quest. He vows to bring the Lords of Shadow, who create the monsters that he assumes killed his wife, to justice, and he does so with the vain hope that he might bring his wife back to life. He braves hell and high water to do so, and he does do some "questionable things" while doing it.
Let's look at some examples:
First, the Black Knight. It's Claudia's guardian. Well, Gabriel goes to sleep one night, has a dream about killing Claudia, wakes up and Claudia is dead. The Black Knight, which up until this point has done nothing in Gabriel's presence but show good will to Gabriel and Claudia, flips out and tries to kill who he assumes killed Claudia. And at that point, Gabriel can't even tell himself "Hey, I didn't do it!" because he's probably sitting there thinking "SHIT, DID I DO IT?" So he fights for his life, likely driven by a mix of self-preservation and a desire to finish his mission, and kills something that has up until that moment been entirely benevolent towards him.
Second, Vincent Dorin. Whatever you think about his deeds, or the concept of "the greater good", Gabriel essentially took the one thing keeping an obviously crazy man alive and left him for dead. And for someone who expresses a vested belief in the concept of mercy and forgiveness (to Satan, no less) that's not a casual act. As the player, we sit there and say, "Yeah, he got what was coming to him" but if/when Vincent dies, Gabriel is at least in part responsible.
Third, Pan. This one is pretty obvious in the game. Gabriel is upset at killing Pan. He does not like doing this, but is forced by Pan to accept it as necessary. Pan sees himself as a sacrifice made so that Gabriel can reach the Lord of the Necromancers and defeat the Lords of Shadow. Pan even tells Gabriel "I've accepted my fate" and asks him "Can you accept yours?" and Gabriel replies "I am not worthy. I am not of pure heart." So right then, it's not a stretch that Gabriel just feels like a straight up murderer.
So after the world's most grueling journey and some tough decisions, he finally gets to the Lord of the Necromancers, no doubt filled with self-doubt only overridden by the desire to see his wife, his everything, again. He gets there and Zobek is like "Hey, you know me, the guy that helped you succeed? Yeah, I'm a bad guy and I killed your wife. Actually, you killed your wife. I made you kill your wife."
At this point, Gabriel is emotionally unstable and is hit with a megaton bomb "You killed your wife." Honestly, it doesn't really matter that Zobek made him do it. I imagine myself in that scenario, and ask myself "If I knew I had been the one who had killed my wife all those days/weeks/months ago, would it really matter if I knew I was mind controlled?" It's like a band-aid on a missing limb. Ok, yeah, Zobek made me do it, but my wife was alive, was forced to suffer through her own husband killing her. And me or Zobek, either way she's still dead. I can only imagine what that must be like. And that Claudia girl I met? She was fine and I came along and killed her too. And the creature that tried to bring her killer to justice? I killed him too. It was my body, my self, that killed them, and had I not been there they might still be alive. And that crazy priest, well he was bad, sure, but I killed him too with the "help" of the Lord of the Necromancers. And Pan? I killed him, he let me kill him, so that I could come here, learn that Zobek made me kill a bunch of people, and that the Lord of the Necromancers was helping me the whole time. All these people are dead in some way because of me. If I had never existed, they all might still be alive. That's
heavy shit.
Then literally Satan comes down from the sky, and is like "I did this." Ok, well I can imagine that if Satan's standing right in front of me, no matter how bad I was, I'm still better than Satan, right? God will grant me mercy. God will grant me justice. So Satan gets fought, Gabriel finally gets his hands on the mask that he's been tearing everything apart for, as is sitting there thinking "I'm forgiven. God gave me this mask so I can bring Marie back."
AND THEN MARIE STAYS DEAD.
Gabriel doesn't even get to die and join her, and Marie tells him he was brought back to life to repent for his sins. Gabriel's probably thinking "Haven't I done enough, Lord? What was the point of all of this?" So he's feeling like a huge piece of shit, angry at God, and then a little vampire girl tells him "Hey, I need your help to stop the end of the world". Gabriel's probably thinking, "Ok, here's my chance. I either earn my redemption or die trying. Either way I get Marie back." Turns out, though, that he still has to kill one more person, throw away his humanity, so even after he's saved the world, he's an immortal monster.
I realize I've deviated a bit, but I think his remorse is incredibly understandable, which makes his Dracula make plenty of sense. If anything, the story tellers are at fault for trying to make Gabriel too much of a stoic badass between certain cutscenes.
Then Lords of Shadow 2 just takes a big, semi-solid, smelly, pea-green dump all over everything.