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...
Being in here, getting into BTC is not a regrettable decision to be honest, there are lots of opportunities and chances that awaits us here, so I don't think that someone will actually regret being in here, unless they did something illegal that revolves around BTC and now that's a definite decision that you'll really regret, but aside from that, I don't think it should even be doubted, and for your friend I feel bad for him, he's not the only one though, everyday there are lots of people that are being scammed, so in the next time, play safe and know who to trust.