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...
No, because in a first place bitcoin is risk investment thing and so it's up to me to invest on what I can only afford to lose and bitcoin has nothing to do with people it's us who took the chance to decide whether we will invest or not people, I think your friend not foresee it well before he/she invest in bitcoin, but then no one is to blame, disappointment is real but your friend still believe in bitcoin.. just keep on trying and do not give up...your time of profit will soon come too.