Hi.
Celebi @ Leftovers - Impish
252 HP / 252 Def / 4 Atk
Seed Bomb / Zen Headbutt
Swords Dance
Heal Bell
Recover
-Swords Dance to up attack.
-Heal Bell means that status does not affect this Celebi much.
-Recover is a solid form of recovery.
-Seed Bomb OHKOs Tyranitar , Swampert , Suicune , Vaporeon and other walls.
-Zen Headbutt kills Machamp , Gengar , Lucario , Roserade and does nice damage to Rotom-A.
-Very bulky, takes pursuit from ScarfTar and OHKOs with Seed Bomb. Scizor is harder to deal with and requires being removed beforehand.
-Magnezone makes great partner removing Scizor and other steels so that they cannot wall this set.
-Any Pokemon who also benefit from having Tyranitar and other things that Celebi can kill are great partners.
-ScarfTran is a great partner together resisting every type and being a good offensive core and defensive core.

Celebi @ Leftovers - Impish
252 HP / 252 Def / 4 Atk
Seed Bomb / Zen Headbutt
Swords Dance
Heal Bell
Recover
-Swords Dance to up attack.
-Heal Bell means that status does not affect this Celebi much.
-Recover is a solid form of recovery.
-Seed Bomb OHKOs Tyranitar , Swampert , Suicune , Vaporeon and other walls.
-Zen Headbutt kills Machamp , Gengar , Lucario , Roserade and does nice damage to Rotom-A.
-Very bulky, takes pursuit from ScarfTar and OHKOs with Seed Bomb. Scizor is harder to deal with and requires being removed beforehand.
-Magnezone makes great partner removing Scizor and other steels so that they cannot wall this set.
-Any Pokemon who also benefit from having Tyranitar and other things that Celebi can kill are great partners.
-ScarfTran is a great partner together resisting every type and being a good offensive core and defensive core.