LO Terrakion doesnt really check Extremekiller anyway, as a solid majority of them run max speed.
Solid Majority? Dont think so. Only 15% use jolly nature. The reason why people dont run max speed is because a jolly nature is required - this means that the frailer mons like mewtwo and palkia will have a chance to survive a +2 extremespeed. BTW if Arceus is at 80% health, they always extremespeed on terrakion as they believe its scarfed. Unless Terrakion suffers life orb recoil earlier in the match, the oppoent thinks that its scarf.
252Atk
Terrakion (Neutral)
Close Combat vs 4HP/0Def Multitype
Arceus (Neutral): 87% - 103% (336 - 396 HP). Guaranteed 2HKO. 23% chance to OHKO.
This is Jolly Arceus, if it takes even minimal damge,such as from Xatu's U-turn or takes life orb recoil, it KOs with close combat. So when its life orb terrakion vs arceus and arceus is jolly, they always use extremespeed.
Now calculation with life orb compared to choice scarf:
252Atk Life Orb
Terrakion (Neutral)
Close Combat vs 252HP/0Def Multitype
Arceus (Neutral): 97% - 115% (434 - 512 HP). Guaranteed 2HKO. 87% chance to OHKO.
252Atk
Terrakion (Neutral)
Close Combat vs 252HP/0Def Multitype
Arceus (Neutral): 75% - 89% (336 - 396 HP). Guaranteed 2HKO.
This is the bulkiest set that extremekiller arceus runs. So when arceus uses a bulky spread, it normally uses earthquake thinking it survives the close combat only to be outspeed and KOed.
Now you may tell me that maybe jolly Arceus will use earthquake vs terrakion etc etc.
This is based on my experience of course so if you disagree, please show some logs. My logs are all messed up and I of course have over 500 battles saved so I cant find them. BTW I dont understand why some of my logs arent saved.