After beating your Machamp, look for the following CP values. These values are those of a Machamp with perfect IV's.
Machamp has 234 attack, 162 defense, 180 stamina. As a Raid Boss, it has a CP of 18144.
Machamp is a Fighting-type. It has access to the following moves:
Other viable counters
For alternative Flying-types, Lugia Charizard, and Pidgeot are your best choices. They also resist Machamp's Fighting-type attacks.
For Fairy-type counters, Wigglytuff, Granbull, and Clefable are your best alternatives to Gardevoir. Be cations when using them, as Machamp has access to super-effective, Steel-type attacks.
For raw damage, use Moltres and Salamence. They have some of the highest attack stats in the game.
For other Psychic-types, Exeggutor, Alakazam, Espeon, and Mew are your best choices. Like the Flying-types, they also resist Machamp's Fighting-type attacks.
IMAGE CREDIT: The Pokémon Company