If you have more medals than someone, you can get 10-20 (depending levels) for 100%.
If you have fewer medals than someone, you can get 20-40 (depending levels) for 100%.
He had fewer medals than you. You are attacking an easy base and are limited on possible rewards. He is attacking a harder base and has more reward potential. It is actually fair that you traded medals for the amount of damage you both were able to do.
Revenging a revenge is always worth 0.
You know you wanna be shady