What are the minimum sets of pieces required for checkmate when the opponent has no other piece that the king?
- King + Bishop + Knight
- King + Bishop + Bishop
- King + Rook
- King + Queen
- and don't forget the unlikely King + Knight + Knight + Knight
Assuming the lone King is attempting to avoid checkmate.
As simple as a Knight or even a pawn, if you consider the fact that your opponent's pieces can block the escape squares too.
W: Kf1, Nf2
B: Kh1, h2.
The Assume that white played Nf2# in the last move. So, white has just used one knight to checkmate black king.
There are many answers to your question, 1) A rook 2) Any 2 minor pieces (Minor pieces: Bishop, Night) 3) A Queen 4) 1 pawn :)