good - bonus!

If you do good work - or do well on a video game - you're supposed to get a bonus.

Chop off the end and you get:

French bon.
Pronounce it "bohn," like you're saying "bone" but have a head cold.

Add a "u" in the middle, "o" on the end, and you get:

Italian buono.
Pronounce it "bwoh-no".

"o" becomes "e" and you've got:

Spanish bueno.
Pronounce it "bweh-no".

Working through the puzzle is a little tricky, so just say:
bonus, bon, buono, bueno - it's a good thing!