Unless I'm missing something, it's because you don't have enough accuracy to overcome her resist.

I stun SC all the time with my Astralon.

You're missing that it doesn't say Resisted in that screenshot.

Is astralon booked?

100% booked. Here's another one just now changed it up for testing. Here Dhukk has less accuracy than Astralon, doesn't get resisted applying the two debuffs. Astralon follows, no Stun. Accuracy is not the issue.

i

tbh, i thought i noticed someting with astralon (mine is also booked) but thought it was weak hits against force (obv not issue here).  I know in doomtower astralon has worked fine (though I've basically auto'd up to 80 so haven't paid alot of attention.  I will watch closely in arena tonight, do u think the issue is just against skullcrown and/or is it just astralon?

No issues with Astralon stunning anyone else in other content. It's Skullcrown, or Astralon interacting specifically with Skullcrown's passive. Here's another just did, I proc the Unkillable, then Brogo is able to stun her after the Unkillable is already up. It's something to do with the stunning at the same time the passive procs is my guess.

@Chill_Dawg, you sure you are stunning her on the would-be killing blow, not before?

If anyone else can test this with other champs that can one-shot her and place a stun I'd love to see the result.

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I just went out to arena and tested it and I can't get a stun on her either now. Granted, I only faced three teams with her, but no stuns.

I 100% have landed stuns on her with Big'un and Brago. Might be a specific interaction with Astralon, I don't have him.

Just tried using Brago to land the killing blow and stun, look carefully the stun would have been placed but you can see part of Remove Debuff ticker showing that Resurgent passive removed it. So I'm convinced that it's Astralon/Skullcrown skill interaction where the stun is not being placed when her passive procs.

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Yeah, I was specifically using Astralon so I think you might be right.

I heard there is a bug with unkillable that affects debuffs. 

Yes it is a known bug

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I guess more people with Skullcrown (not me lol) are happy with this bug, than those (me) trying to stun her.  Curiuous, is this only for skullcrown? Only in Arena?  Obviously doesn't happen in CB, at least not for Skullcrusher.

I don't think it's unkillable specifically. I guarantee you that I can place stuns on unkillable buffed champs.

I think the problem is the way that the unkillable buff works for Skullcrown specifically - namely, that it triggers when her HP drops below 20%. That specific interaction seems to be bugged.

AFAIK, she's the only champ with a procced unkillable buff. However it could very well happen with the Swift Parry artifact set as well, if this is truly the bug.

Interesting, if I had anyone in swift parry I would try and test