Abby Lockhart (Maura Tierney), ER
If Carol had struggles, then Abby was in an all-out war with her personal demons, which included alcoholism, infidelity and a bipolar mother among other things. Oh, and let's not forget that she survived chopper crashes, kidnappings, a smallpox outbreak and ambulance bombings. Through it all, Abby, who eventually earned that M.D. suffix, remained sympathetic and empathetic, thanks in large part to Tierney's superb acting chops.