Change Riven's Ult description to % missing HP.
This is definitely an OCD thing, but here we go. Riven's ult description could be changed. Every other ult that has this mechanic just says "X% of the enemy's missing HP" or "+1/2/3% bonus damage per 1% missing HP". How about instead of 80/120/160 (+60% Bonus AD) to 240/360/480 (+180% Bonus AD), just change it to 80/120/160 (+60% Bonus AD), plus 2% damage per 1% of the enemy's missing HP. It does the EXACT SAME amount of damage. I don't see a huge counter-argument to this, other than "It's not necessary".
Let me know if you care.