The most notorious feats in 5th Edition D&D are Sharpshooter (SS) and Great Weapon Master (GWM). These feats are considered the most powerful because of a mechanic they share in common. Yet, a common "fix" to nerf them does not have the intended result! Let's run the numbers.
Elven Accuracy gives you "super advantage" via a mechanic that lets you select the best of three dice rolls when you have advantage on an attack. This is widely regarded as a very strong, if not broken, feat. The truth is that the "super advantage" part of the feat doesn't do that much, because already having advantage is normally good enough.