If its only haki then Shanks or Primebeard.

Gotta be Goatbeard, but Shanks is a close second.

If it's Haki then shanks.

Just Haki? Probably Shanks then.

Thought it meant just normally

Haki-wise it's Shanks.

Shanks is the strongest character ALIVE. Primebeard is stronger

It's Luffy. The post says "all at their prime" meaning this is prime Luffy with mastery over his fruit and likely has insane haki just like Joyboy (likely more powerful than Joyboy's).

This kinda makes me happy how some ppl is picking Big Mom more than Kaido. Even though Kaido's overall haki is better than Big Mom's, BM is very underestimated, so I don't mind her winning this.

Gotta be prime beard then shanks, shanks a close second because of his haki

This is just in terms of Haki, so Shanks wins. Otherwise primebeard wins.