Hmmm... most of mine are already mentioned, so I'll just throw in Andrea in the Walking Dead TV show
In the comics, Andrea is easily one of my favorite characters, just because she's a good blend of competent and badass as the sniper of Rick's group, while still feeling like a very real person.
In the show, most of those traits are thrown out and she spends most of the time being annoying or making dumb decisions. At the same time, though, Carol seems to be getting the reverse treatment, as she wasn't a very strong character in the comics, but is stepping up to fill in comic!Andrea's shoes for the show.