I got three sweeping sets.
Role: specially defensive physical sweeper
ability: Both are good so doesn't matter to me.
EVs: 252atk, 248sp def,8hp
item: Assault vest
Poison jab: stab and 30% chance to poison
aqua tail: coverage against ground types
Sucker punch/x-scissor/crunch/night slash/knock off: Sucker punch is priority if your opponent plans to use an attack, X-scissor provides extra coverage against dark types, Crunch has 20% chance to lower defense, night slash has high crit ratio, and knock off deals double damage to those who have a held item and gets rid of held item after attack. All cover psychic types.
earthquake: Coverage against steel types and rock types
Role: Bulky physical sweeper
Ability: doesn't matter
Evs: 252 atk, 252 hp/252 def, 4 speed
Item: black sludge
coil: Raises attack, defense, and accuracy all by one stage.
Iron tail/earthquake/x-scissor/sucker punch/knock off/crunch/night slash
Role: specially defensive special sweeper
Ability: Inconsequential (not important)
EVs: 252sp atk, 248 sp def, 8hp/speed
Item: Assault vest
sludge bomb/sludge wave: Sludge bomb for better chance to poison or sludge wave for slightly higher power.
Giga drain: Steals hp from foe. Coverage against ground and rock types.
Dark pulse: 20% chance to flinch. Coverage against psychics
Flamethrower: 10% chance to burn target, Coverage against steel types.
Overall seviper isn't exactly a good Pokemon competitively but he does do pretty good in NU tier.