Interesting question, I know. For me personally the answer is no - I have not ever regretted having gotten into bitcoin, despite having spent hundreds and hundreds of hours researching the topic. It's always been an interesting ride.
But I have a friend who got scammed and he regrets having had anything to do with crypto in the first place. It's pretty sad but there's nothing I can do about it. I even offered giving him half of the amount he lost from my own crypto stash (mind you I am not rich) but he's so scared that he's not interested any longer...
Your friend is a person who cannot fight or endure the bad things he has experienced, he should be able to fight for and keep trying to get it back, because in every test or trial there must be something good there. In fact, I personally have been a victim of fraud several times when I was first in Bitcoin, but after I kept on going and trying for the best, in the end I got a good profit from Bitcoin. Believe me, bad events at the beginning will not be possible to continue, the most important thing is that you must have the desire to continue to fight and learn for the best, because regret will only make you worse if you don't fight.