After beating your Breloom, look for the following CP values. These values are those of a Breloom with perfect IV's.
Breloom has 241 attack, 153 defense, 120 stamina. As a Raid Boss, it has a CP of 18174.
Breloom is a Grass-type and a Fighting-type. It has access to the following moves:
Other viable counters
Fairy-type attacks also deal super-effective damage. Granbull and Gardevoir are the best Fairy counters. Be wary of a Sludge Bomb, though.
For alternative Fire-types, Entei, Charizard, Blaziken, Typhlosion, Flareon, Houndoom, and Arcanine are best.
If you're looking for a Poison-type, go with Muk. If you're going for raw damage, Dragonite and Salamence are best.
Articuno is the best Ice-type counter. Pidgeot can be useful as a Flying-type counter. Espeon and Alakazam are the best alternative Psychic-types.
IMAGE CREDIT: The Pokémon Company