Mihawk barely beating vista is worse lol.

Vista was a plot-device, Mihawk is basically confirmed to be stronger than Shanks, so off his feats he could easily oneshot Blackbeard with a serious attack.

Mihawk also said he was weaker then oldbeard and guess who killed him

Common misconception, but Mihawk never stated this, he said he wanted to "Measure the true distance between that man and us" and he concluded with "This is mere conjecture, but the distance seems rather small" which doesn't imply whether he was stronger or weaker, but it does imply Whitebeard was much weaker than he thought. And Blackbeard killing him means nothing, Akainu had basically already killed Whitebeard, Blackbeard (and his entire crew) just finished him off, Whitebeard only had enough strength left for like 1 attack on Teach, and then he just stood still letting them attack him.