Hi there!
One bug that is present for a long time now is with Nightcrawler. He is disappearing in the middle of the fight. when he evades he becomes totally invisible for a while. During that time he knows to do heavy attack and I have no idea that he is about to do it because I do not see it coming since he is invisible! I took a screenshot to show you. See in the image he is hitting me while invisible...

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This is not only me, many people complain about it, and it makes already a hard champion to fight even harder...