I imagine Wolverine still scares some of his lower-tier villains. Or, at the very least, frustrates them. Dude just will not die. That's gotta be annoying.
The Hulk is definitely still carrying the title for king of the scary heroes, though. I remember an issue of Captain Marvel where Genis (before he went crazy) wound up fighting the Hulk. Dude is a cosmic hero, which generally means he deals with higher-power threats in the first place, and he had the Hulk's buddy Rick Jones in his head helping him out, and he was still practically wetting himself. Then the Wendigo showed up and I think he might actually have wet himself.
The Sentry, being bats*** insane, probably scares people too. I'd certainly be scared if the media were calling a vastly powerful guy with known mental conditions a "hero" and giving him free reign to use his own judgment when fighting villains or other heroes. Same goes for Deadpool and all the other crazy sons of b****es in the cape-and-tights set. You never know just what a crazy person's gonna do.