Alec is fascinating and I have the following opinions on him:
He ended up a stunningly good person when you adjust for his starting position, but a terrible person by every other useful metric.
The fact he's a talented artist should have been explored more.
He would fucking thrive on Tumblr, given that his hodgepodged ethical system consists basically of hurting whoever he's picked up on as being "okay to hurt-" essentially reverse-engineering his morals from shitty pulp revenge novels and whatever it is his friends want. He's playing a part because he feels like he should, he does terrible things when the option seems open but doesn't seem particularly attached to doing terrible things; the Undersiders aren't holding him back like a dog on a leash, instead he periodically touches base with them about how terrible they're willing to let him be to resolve the current situation, and then he often takes their wishes seriously.
One of the fun background tragedies of Worm is how Taylor doesn't seem to notice how much Alec cares about his relationship with the Undersiders specifically. He's genuinely really hurt when Taylor advances the idea that he might be on track to turn into a replica of his father. It comes out of left field for her when he throws himself in the line of fire on accident. Taylor not really being aware of how much she's influencing Alec's decisions, in a twisted way, is the lynchpin of the Sophia mess.
An underremarked upon detail- Alec was part of the undersider's pre-taylor unanimous decision to help fight the endbringers if it ever came up, and then he followed through on that, even though he knew he'd probably be useless. Even if he literally can't care about people the normal way, he really badly wants to, and I think a lot of his behavior maps a comprehensive attempt to emulate what he thinks someone who gives a shit should do. Which, at a certain point, just turns into giving a shit.