“The pain was just unbearable!”

You got your wisdom teeth removed last week and had to stay home because of the pain. Now you're back at work, and making small talk with your boss. You tell her about it.

The pain was just unbearable!

just (adjective)

When used in this way, "just" means "very" or "completely". It can be used with positive or negative adjectives:

They did just a phenomenal job on this event.

This was just a horrible, horrible idea!

unbearable pain

If you can "bear" something, it means that you can "stand" it or survive it. Something that's unbearable is too bad or difficult to accept. 

"Unbearable" pain is really strong pain that makes you cry, scream, or feel like you're going to die.

Other things that are "unbearable" include:

• unbearable heat
• unbearable suffering
• unbearable tension (in a stressful environment)
• unbearable conditions