Chross - The Art of Mainstream Spankings

Original title: Kiru ra kiru: KILL la KILL
From Season 1, Episode 9: Chansu wa ichido or Once in a Lifetime Chance
As best I remember, this series consists of the main character having various video game style "boss fights" in this episode it's a sort-of tentacled monster (guess there's gotta be at least on in an anime) and this monster uses it's tentacles to literally whip the main character's butt. Clip (English dub): https://mega.nz/file/zUAV3Jqb#1w-vyLRIc ... HiSwcW2yxY

Verys unusual spanking scene and method, but I enjoyed it!
It's episode 9 and Ira Gamagōri is really having his way with Ryuko Matoi.