Why can't i stun attuma using sinister?

TorgoNudho

Hello gang

Sinister's purify down ability is supposed to counter skill champions ability to purify debuffs. How come this can't apply on attuma? I couldn't stun him in the monthly eq.

whyme_why6

Becauses attuma's ability accuracy is reversed so instead of something lowering it, it gets raised and when some raises it, it gets lowerd