This is a problem that should not be 'taken lightly'. [=this is a problem that should be treated seriously]
Considering the harm he did, he's 'gotten off lightly' with only a warning.
Our troops were armed too 'lightly' to take on the heavily armed invaders.
(..) I’m overwhelmed, sir. But the council elects its own members. They’ll never accept this. I think they will. They need you. More than you know. YODA: Allow this appointment lightly the council does not. Disturbing is this move by Chancellor Palpatine. I understand. You are on this council, (..)2005 Star Wars: Episode III - Revenge of the Sith