IMO Taka falls on the neutral axis rather than evil. He very clearly expresses regret and unease about the crimes he has to commit, and while he will still follow his father's orders (to some extent), there have been instances in which he either sabotaged himself to help you or outright helped people on his own accord.
To be on the evil axis he would have to be more indifferent. He wouldn't try to save lives unless it was for his gain. None of the 'good deeds' of his have so far been to his benefit. They all made him look worse in the eyes of his father/Meteor as a whole, since his constant inability to actually stick to the cause has given him the reputation of being unreliable and a failure. Taka doesn't harm people because he thinks it's okay or necessary. He tells you he doesn't agree with any of it. It's all because of Solaris' influence.
Taka's simultaneous regret about his actions but inability to outright stand up against Solaris makes me think he's a better fit for a borderline Lawful Neutral/True Neutral... not sure about his tendencies - he occasionally does rebel against Meteor, but he doesn't have the guts to really go through with it.
He has moral objections against Meteor's methods, and if he is given the necessary freedom, he will act in ways that will benefit the player. Telling you where to find the next PULSE (he plays it off as a trap in front of Corey, but it's pretty transparent that he knew you could destroy the PULSE if you found it), helping you in the WTC (ordering grunts to care for Amaria, changing water levels, giving you the option to not fight him despite knowing it will likely get him punished).
He doesn't have what it takes to completely disregard his father's orders and go his own way, but I'm hesitant to put him as Lawful because none of his loyalty feels genuine. He has been pressured and raised into following Solaris' beliefs and plans his whole life, and it clearly left him dependent on his father's approval - but it's easy to tell that nothing else of it all really matters to him. His entire speech to Tania in the WTC is summed up as "I know I'm doing shitty things that I don't actually agree with, but dad says so". He's obedient entirely as the result of abusive parenting.
He feels obliged to follow his father's authority, but certainly not out of a pure belief that it is the right thing to do. We have seen that lack of belief in action every time he defies Solaris, however subtle. Solaris is very much aware that Taka's heart isn't on the mission.
@Ice says he considers Taka chaotic neutral, and I can definitely see him heading that way - but right now, at this point in the story, he hasn't made that development yet. He still hasn't snapped out of his obedience, but if he manages to, I'd agree with that alignment.