Thanks for all the comments!
Changes:
Slowbro -> Swampert
Swampert @ Leftovers
Trait: Torrent
EVs: 248 HP / 252 Def / 8 Spd
Impish Nature
- Earthquake
- Stealth Rock
- Toxic
- Roar
Per the advice / comments of TheEeveeAnimations, Kitten Milk, and Patrick1088, I've changed Slowbro to...