nezahvalno

1. ungratefully
   Posle svega što smo uradili, ponašao se nezahvalno. — After everything we did, he behaved ungratefully.
2. (nezahvalno je + inf.) it's a thankless task; it's tricky
   Nezahvalno je predviđati rezultat ove utakmice. — It's tricky to predict the result of this match.
   Uvek je nezahvalno upoređivati dva pisca. — Comparing two writers is always a thankless task.