pun
This is a play on the word unleash. In order to free a dog that is tied up you need to let it off the leash, or "unleash" it. Generally, the word unleash is used to set something free. In this case the dog's potential needs to be unleashed or set free in order for Ryder to see what the dog can do.
A paradox is a contradictory statement.
An oxymoron is a statement of opposities (jumbo shrimp)
A malapropism is a word that is misused because it sounds similar to the correct word for the sentence.