Like hell

Like hell is an expression which changes depending on how it's used.

If you use it after a verb, it works like an extreme adverb. A few examples:

When the crew saw the bear, they ran like hell. (They ran really fast)

"I closed the door on my finger this morning... It hurt like hell!" (It hurt a lot)

We tried like hell to prevent the highway expansion, but we failed in the end. (We tried really hard)

On the other had, if you use like hell alone, it's an exclamation which means "no way" or "absolutely not." Here we go:

You to your colleague: "Bob's going to tell our boss that we're not going to the offsite because we don't believe in offsites."

Bob to you and your colleague: "Like hell!" (No way, I would never do that.)