Evan Hansen is probably the hardest male role ever written. This becomes quite apparent when you see what the role has done to Platt. He's on a strict diet, constant vocal rest, and sees a physical therapist in order to keep him from permanently picking up Evan's ticks. Say what you want about the show, but the role is almost physically impossible to play. Some Honorable Mentions: Hedwig, Billy Bigelow, Sweeney Todd, Tevye, George (SITPWG), Che, Bruce Bechdel, and honestly, all of the men in Falsettos. That show is HARD and EXHAUSTING.
Evita is probably the hardest female role. The role is a vocal shredder. I don't think I need to elaborate. It's crazy. Some Honorable Mentions: Trina, Big Edie/Little Edie, Caroline Thibodaux, Nellie Lovett, Dolly Levi, and I'm sure many others that are completely escaping my mind.