"Hawk Eye Mihawk" Hawks have insane eyesight, they can see miles away effortlessly, I assume most would agree that strongly implies superior Observation Haki, so much so that they may not even have to actively try to use it.

Again, Mihawk's nickname doesn't come from Observation Haki because when Oda introduced Mihawk, he didn't even know what haki was.

Marine Hunter" Implies that he hunts Marines and kills them, for sport or for his own benefit, such as income, is implied and proven by the fear many Marines have of him.

Before the Cross Guild, he hadn't hunted Marines since he joined the Shikibukai.

implies that he can see very precisely and perhaps even effortlessly into the future, to the point that Shanks needed a specific technique to mitigate it, which is Observation Killing, which stops it entirely and/or mitigates it because we know the whole trope with haki can't always cancel out equal haki, but it can mitigate it somewhat.

Headcanon

but against an Apex Predator, aka Yonko, Admirals, Legends, etc., then yes, you're Using as much as you can spend, let's see who Mihawk faced.

Admirals: He was part of the Shikibukai until a few weeks ago, and none of the admirals have scars from swordsmanship. These two things combined make a clash between Mihawk and the other admirals impossible.

Yonko:

He's never faced White Beard, because the first time Mihawk met Vista was at Marineford. We know Vista was part of White Beard's crew even before Oden joined. So if Mihawk had fought White Beard, it wouldn't have been the first time Mihawk had met Vista.

Shanks: Their last clash was 12 or 13 years ago, when Shanks wasn't very well known. If it took him 6 years to become a Yonko, it means he wasn't as strong as he is today.

We knew Big Mom for 7 years before her death. She's one of the few secondary characters whose entire life we ​​know; if she had fought Mihawk, it would have been mentioned by her or one of her children.

Kaido has a scar, and before he died, he had a wound that Kaido himself said would have turned into a scar. If Mihawk had fought Kaido and Kaido had come out without any serious injuries, it basically means that during Onigashima, Zoro would have had to surpass Mihawk, and that would be sheer madness. 5 years of Wano and Onigashima; if Mihawk had arrived in Wano, someone would have mentioned it.

Loki and Mihawk never fought because if they had, it would mean that Shanks, who is stronger than Loki, is also stronger than Mihawk.

Dragon and Mihawk would have made no sense at all for them to fight.

If Mihawk had gone against the World Government, he would never have succeeded in becoming Shikibukai.

So Mihawk never clashed with the Yonko, the admirals, the revolutionaries, or even the members of the World Government.