Broken Ribs>Hit buy bullet with no protection on
The energy from the bullet upon hitting the vest is diffused throughout the material, thus slowing the bullet down, but also putting immense pressure on your ribs.
EDIT:
Broken ribs hurt like a bitch.
But still people think kevlar makes you invincible.
It's also heavier than forget.
EDIT2:
Also alot of bullets can pierce kevlar