Rockslide machamp
Rockslide has an energy cost the same of ancient power, but more power. in PvP
How does this affect machamp in PvP? Counter is an absurd fast move, with high EPT and good DPT. Having a very fast charge move that lets it deal with a large number of its defensive coutners; Flying, fairy, ghost, poison, bug, psychic, and seemingly will go well as a shield breaker.
How does this affect machamp in ultra league and masters, as well as to a smaller extent gyms, as now dragonite, gardevoir, togekiss and gyarados dont resist it if its got DP and RS
Answers
For gyms it is great and a must-have in my opinion. Many times it will be best to plow through a gym than change your lineup due time and the risk of the defending trainers noticing and gRazzing. Machamp, already being one of the prime gym sweepers, really benefits from not having to back out when facing some of its counters. Not the beat -all solution, but definitely a great improvement.
It's somewhat relevant for master league. Machamp isn't a top contender, but it is apparently playable for hard countering Tyranitar and previously you needed to have one with legacy Stone Edge to have a way to hurt Lugia, Dragonite and Gyarados that might come after the Tyranitar to eat Machamp. Rock Slide is straight up better than Stone Edge, so this seriously reduces the trading worth of those legacy Champs.
Machamp's CP is still on the low side and it'll lose every single neutral matchup, but at least it has an additional tool now for some of the bad matchups.