Diavolo is considered a very powerful Stand user, but the fact that he was defeated by Gold Experience Requiem, a completely broken Stand ability, makes him seem stronger than he really is. He has several weaknesses to his ability.

First of all, neither time skip nor Epitaph make him any better at dealing damage. If you are simply so tough that King Crimson can't hurt you, Diavolo can't beat you.

Second, King Crimson actually has a stamina limit. Attack Diavolo enough times in a row and he won't be able to use time erasure to escape his fated death.

Third, it may seem like Diavolo is invincible and intangible within erased time, but he actually isn't. He can still see within erased time, and he still breathes within erased time, making him vulnerable to auditory and visual attacks. The visual part applies to Epitaph too, since Epitaph isn't telepathic. It duplicates photons from the future via a projection onto a nearby surface, such as Doppio's hair. This means a sufficiently bright light-based attack will blind Diavolo even from the future! This is the same concept as using an info hazard type ability against any other precognitive. Additionally, the fact that Diavolo still talks and breathes in erased time means that he can't erase his way out of a toxic gas attack.

Fourth, Diavolo isn't actually using Epitaph 24/7. If you catch him while he's sleeping, he is totally defenseless.

Fifth, you can attack him immediately after time is done being erased. In Vento Aureo, his enemies didn't have a lot of luck with this since they didn't actually do a good job at keeping track of time.

Sixth, his range is pretty terrible. If you can wear him down with enough long-ranged attacks and kite him from a distance, you have a very good chance of winning against him.

Finally, his ability only erases 10 seconds at a time. A slower, harder to notice, damage over time based power will affect Diavolo even as he erases time. This can be seen in the Metallica fight, where Diavolo would have eventually succumbed to iron deficiency if he didn't consume Risotto's liver.

All of these offer a good way to defeat him without resorting to another broken power, but they do require you to have some knowledge of how the ability works beforehand. In the end, King Crimson, while very strong, is actually quite manageable to defeat if you have the right powers and know what you're doing. Some examples of other Stands that could defeat it via the above methods are Vitamin C (damage over time effect), Jail House Lock (not immediately noticeable, prevents Epitaph from working effectively), Purple Haze (damage over time), Heavy Weather (through a visual effect that persists in erased time), Ciocolatta (large range and slow acting effect), and Doobie Wah (too persistent, can't be damaged by Diavolo, works through breath, AND too long range).