All the ones I applied for in Oct. and Nov. 2018 (I thought my reports were clean but I jumped the gun- should have waited until December)
I actually have two that I regret, one in the early rebuilding phase and one more recent.
When I began my rebuild I applied for the USAA Secured Card without doing research. I did not realize it would never graduate and ended up with a substantial amount of my own money tied up for a credit card that would never grow. It has since been kicked to the curb.
My most recent regret is Paypal MC. It is just meh to me, at best. I'll keep it around for the utilization padding, though.
I had Capital One's Platinum Visa from 2005 to 2010. The card came out like two years earlier, and IIRC, was the first Visa/MC to bare the "Platinum" designation. Visa/MC "Gold" cards had already been around for a while. Anyways, to this day, the only blemish in my credit history was a single 30-day late pay reported by CapOne that I tried to dispute due to mail theft (snail mail payments back then). That derog fell off 15 months ago, but I still have a bad taste in my mouth for them. I regret opening an account with them. They still sends me mail offers.