Mewtwo Powerup

Yup. A strong candidate I would say. Unless you have others (emphasis on plural) with better IV, I don’t see why not

At level 40, the difference between your Mewtwo and a 100% Mewtwo will come down to 4 hitpoints, and that's it. Personally, yes, I would invest in it since I consider the attack/defense IVs to be more important than stamina.

If you've been regularly getting EX passes, there's nothing wrong with holding out to see if you get a better one, but the one you have is also a good candidate for powering up.

Better send it to the professor for evaluation.

In all seriousness any Mewtwo with 15 attack is worth powering up.

To quote the Bit from the original Tron movie:

Yesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes (replaces ctrl and v keys) yesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyesyes.

Yes.

Freakin' yes. 18 EX-Raids and still nothin that good.

In my group of four players two of them have 98%s and the other caught a 100% yesterday.

saltsaltsaltsaltsaltsaltsaltsaltsaltsaltsaltsaltsaltsaltsaltsaltsaltsalt

What is a Mewtwo?

Seriously, yes.

Yes, 15 attack.

I caught the same one, and maxed it out. Although, I have done several more ex raids since, I haven't caught a better one, and have no regrets.

Only if you think you would benefit from a decent raid filler or a subpar alternative to Machamp.
I did max a one similar to yours but, even though I don't regret having a 3960CP Mewtwo, I wouldn't do it again.