First mewtwo worth power up?!

I think you mean 10s, not 19
Currently, there is a very minimal need for mewtwo given current raids
Its worth for powering up depends on what you already have, if you dont already have a ghost/or fighting type type attacker shadow ball or focus blast mewtwo will be worth it to power up, considering it is a max attack and that is all that really matters for dps, but if you already have a strong Bite/crunch tyranitar or two, I wouldn't power it up as they can handle what shadowball mewtwo covers, and a decently strong machamp/haryama can do what focus blast covers, the gen IV legendaries (or the gen 3 weather trio) also can use the candy more (in particularly Giratina for ghost type offense), and its psychic set, while the ebst psychic attacker in the game, doesnt really cover anything outside of machamp raids, and the far cheaper to power up espeon can do that job

However what you wish to do with it is ultimately your decision

If you don’t already have a maxed out Mewtwo, do it! I maxed out my first caught Mewtwo.. it was a 78% with 10ATK.. sitting at 3869CP.. but hey it was my first! I use it as my psycho cut/focus blast attacker.. where my ones with 15A all have confusion/shadow ball.

I'm having the same debate right now over my first Mewtwo, which is 14a 15d 12s but also has a really bad move set so might require some TMs to get decent use out of it. My plan is also to power it up to level 30 for now.

I had one that was 14-12-14 and I powered him up to 30 like right away being my first one, don’t regret it. Has some nice bulk against Machamp and is just cool. Meta relevant right now? Not entirely