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...
It is indeed a sad experienced for your friend. However I think bitcoin has nothing to do with that it is the person behind the investment that needs to be blame not entirely the bitcoin yet I really can't judge him because I don't know the whole story and what he feels. For me, as of now, I don't regret being involve in here although I spend a lot of time in here I still think that iy is good for me too and worth trying for.