Yes, it was in a webtoon. A person was getting punched when he said it so I was thinking that it was like 헉 but i wanted to make sure so that I don't misunderstand in case it had a slightly different meaning

I think you definitely saw these words on comic books, didn't you? I guess '드헉' is derived from '뜨악' or '헉'. I don't know the context where it was used. But it usually means gasping. Sorry If my english isn't correct.

The first one is an onomatopoeia --it's the sound of someone/thing being hit. It's not a verb.