There are hints to his past in his dialogue with Rubedo, but most of it is shown in Episode 2. Guy had an incredibly troutty past. As I said, judging Albedo's character in Episode 1 as his whole character would be like doing the same for Grahf by skipping the second disc of Xenogears.

Conjoined twin to Rubedo, he has a codependent relationship with his brother which is shattered the day he learns that due to his regeneration powers, he's going to outlive all of his brothers. In fact he may technically survive to see the end of the universe and beyond since it's heavily implied that his consciousness it tied to his very atoms and even having them disassembled and scattered across the cosmos wouldn't actually give him true death. Obviously this does a number on his already fragile psyche. He becomes even more protective of Rubedo until Rubedo "betrays him" by showing feelings for other people like Sakura Mizrahi. Episode 2 implies Albedo murdered Sakura, but the DS remake (which gave Takahashi more control of the writing) retcons this to having Sakura save Albedo from being corrupted by U-DO at an earlier point. He's happy she's dead, but also feels guilty because of how much her death hurts Rubedo. When Rubedo realizes that the plan during the Miltitan Conflict for the U.R.T.V. units is a suicide mission that is guaranteed to kill them all and possibly all of Miltia; Rubedo breaks the link between his brothers which makes them all fall prey to U-DO's influence that drives all of them mad. Rubedo and Nigredo are not affected due to having built in immunity but Albedo and the clone brigade are not so lucky. He tries to kill Nigredo because he figures out what he really is (a fail safe to kill Rubedo and a surrogate body for Yuriev to body surf into) and Rubedo has to fight him off and leave him broken on Miltia where they abandon him. He gets rescued and raised by U-TIC but comes up with his own goal which is ultimately to finally be killed off for good. So he plans on re-hooking up with U-DO because he knows that if he merges with it, then Rubedo would finally be able to kill him with his powers since U-DO's power could overwrite Albedo's immortality. Come Episode 3, we discover that Albedo's true desire, which is inadvertently granted by Wilhelm making Albedo into a Testament, is that he wanted to merge back with Rubedo since their story revolves around this idea that the two of them were always meant to be a single being. Sadly, we lost out of the power up this was to give Rubedo because allegedly, their re-merging would have aged Rubedo up to his brother's physical form.

Albedo's who schlick is how troutty immortality really is. He pretty much tells the player this while he's torturing MOMO because to him, pain is the only thing that makes him feel alive. I mean our whole structure of society and living is based on the aversion to death. If you can't die, what point does pain, empathy, bonds, and creation hold?