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...
If guess your friend got scammed by investing through third party who offers high rate of returns by managing his crypto currency investment. First of all we must bear in mind that never entrust any investment to anyone manage your own investments to avoid scam. It is really regretful if he trusted third party investor. Good thing i had never done that I do analyze first before investing into something.