An oxymoron is a figure of speech that uses contradictory terms in conjunction, which means words that don’t appear to go well together. This is good as you can teach your students antonym words and show them the comparison clearly.
Some examples of oxymoron are:
Act naturally
Almost exactly
Alone together
Clearly misunderstood
Diet chocolate-cake
Extinct Life
Freezer burn
Good grief
Living dead
Minor catastrophe
Near miss
Passive aggressive
Pretty ugly
Sweet sorrow
Small crowd
Terribly pleased
Working vacation
p/s : know English is to love English!!