Here's a fun little set I made for Haxorus:
stronk (Haxorus) @ Trailblaze
Ability: Mold Breaker
Tera Type: Steel
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- First Impression
- Swords Dance
- Earthquake
- Iron Head
Might work, or might not. I haven't really tried it at all yet, but something to maybe make Haxorus a threat on the field. First Impression is strong, priority, and gives it a speed boost. It's somewhat bulky, so it can maybe live a hit to Swords Dance. This would probably only work if First Impression actually kills something, but something to think about. Tera Steel helps the bulk since Flutter Mane is running amok with Draining Kiss shenanigans, and all the other First Impression users, plus boosting Iron Head.
You could probably run Tera Dragon + Dragon Claw instead if you want just a full-force attack, but either or would probably work equally well.
I love my boi too much to not try to make him viable.
Edit: I should probably emphasize, this set is pretty situational. Glimmora is a great opportunity to set up, since Tera Steel resists Power Gem and Energy Ball, as well as the immunity to Sludge Wave/Bomb. Usually they will click Sludge Wave/Bomb, or just set up hazards.