100% Machamp C/DP!! But wtf CP?!
Answers
It depends on a lot of factors. Some key ones are how much the Machamp would improve your existing lineup against defenders you see in gym. And how valuable the time, stardust, and candy required to power it up is to you.
If it was me personally, I would keep it, but would hold off on powering it up. I prefer alternatives to Machamp against Blissey and Snorlax, particularly B/SE Tyranitar. And the 100% C/DP Machamp would only offer slight benefits above my existing lineup against Tyranitar, so not worth the cost to me.
Dust is too valuable to use on attackers IMO. I would not power that up but Machops are very common where I am and I already have a low IV Machamp L30 I evolved from a level 30 machop. I dont even use Machamp anyways unless im taking down a gym has 3+ Blisseys and my Dnites are in gyms. The only use for it is Trex with Bite at least for me.
And then there is the nerf issue. I have some level 34+ mons I regret powering up which include Arcanine 91 FF/FB & 91 B/FT, Eggy x3 C/P, Poliwrath 100 Bbl/S and a Vape WP. Sorry to bring Hatorade to your party lol.
What you have there is one of the best attackers in the game. I have two Machamps with the same moveset (2650cp and 2826cp both 90%+ ivs) and they are used to take out the Blisseys, Snorlaxs and Tyranitars that populated my local gyms. I would definitely spend dust and candies on that one if I were you.