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...
I have never regretted entering Bitcoin because I have gotten many things with Bitcoin. not only money but also knowledge and technology. and I think we cannot force other people not to regret they have the right to accept or reject bitcoin. maybe your friend has spent his savings but is not profitable. We can make this lesson in crypto investment, we cannot trust anyone. we have to do our own research. and invest as much as you can to lose.