(NoSpin&Defog)
Qwilfish @ Black Sludge
Ability: Swift Swim
EVs: 4 HP / 112 Def / 252 SpA / 140 Spe
Timid Nature
- Hidden Power [Grass]
- Taunt
- Sludge Bomb/Sludge Wave
- Toxic Spikes
The main idea is bulding a versatile Qwilfish's set, adding to its peculiarities that is OHKO a spinner like Kabutops; In fact Qwilfish's attack is better but also its decent SAtk could be used fruitful. Then Toxic Spikes and Taunt to set entry hazard and prevents an opponent from laying entry hazards down, wish + protect, defog, etc.
Then with a Timid nature and maximum SAtk, you can OHKO Kabutops with SR.
140 Spe is exactly what it needs to be faster than it. Checking on RU speed tiers, we could find an appropiate EV spread to outspeed other 'mons.
Finally, Sludge Bomb/Sludge Wave is STABs move, you can select it aggording to chance to poison/power respectively.
Some calcs:
252 SpA Qwilfish Hidden Power Grass vs. 0 HP / 0 SpD Kabutops: 204-244 (78.1 - 93.4%) -- 31.3% chance to OHKO after Stealth Rock
252+ Atk Life Orb Kabutops Stone Edge vs. 4 HP / 112 Def Qwilfish: 235-278 (86.3 - 102.2%) -- 18.8% chance to OHKO