Unique v only

What's the difference between unique and only? 

Source: Damiano Baschiera on Unsplash

 

Unique suggests that something is unusual or different from other things

• Venice is a unique city. There's no other city quite like it.
• In my opinion she has a unique voice. She can sing all different styles of songs.
• This property is a unique opportunity. It'll sell quickly.

whereas only suggests just one.

• I am the only one who hasn't had a holiday this year.
• The car is the only way to get there. There's no public transport.
• You are the only person I care about.

It's the unique reason why I continue going. 😡

It's the only reason why I continue going. 😍 

Write some of your own examples with unique and only.