In retrospect, BASIC. GW-BASIC, then Borland Turbo BASIC and QuickBASIC.

I don't hate the languages themselves and they were products of their time.

I hate that I spent a lot of time on them in my early programming days on MS-DOS and Windows, before the Internet and before I learned about Linux.

I could have instead used C earlier. Or maybe a PC version of Lisp had I known about Lisp back then.