Grimmsnarl and Hatterene raid time, and here's a set that works for both of them:

Kingambit @ Shell Bell
Ability: Defiant
Tera Type: Steel
EVs: 252 Atk / 128 Def / 128 SpD
Adamant Nature
- Snarl
- Brick Break
- Iron Head
- Leer / Swords Dance
Snarl weakens Hatterene's Mystical Fire, which procs your Defiant boost. Brick Break removes Grimmsnarl's Screens. Leer lowers Defense, while Swords Dance boosts your Attack, although Leer is better since it combos well with your Defiant boosts. Keep in mind Leer won't work on Magic Bounce Hatterne. Both Pokemon have attacks that lower stats (Mystical Fire on Hatterene and Spirit Break and Play Rough on Grimmsnarl). Since they're both slow, you'll be faster than both even with no Speed investment.
If you have more than one Kingambit, you can make one full Def and one full SpDef rather than mixed bulk, and you can run SD alongside Leer on both, swapping out Snarl vs Grimmsnarl and replacing Brick Break vs Hatterene.