One word for a "very tough task"
Let's get downright crude here: It's a bitch to talk politely with a person who's rude to you. Typical idiomatic American street talk and locker room lingo. Also heard in classrooms, at sidewalk cafes, and other places where American speakers congregate and jawbone.
If you want alternatives to tough as an attributive adjective, you can take your pick from hard, difficult, irksome, challenging, strenuous, laborious, uphill. All can be used predicatively as well, except the last.