Blue
Ravenous Bugblatter Beast of Traal
One of the aspects of 5e that I see the most complaints about are the feats that give +10 damage for -5 to hit.
By changing the wording to allow a player to choose the level of the penalty to hit, limited to a maximum equal to the character's proficiency bonus, and gaining a bonus to damage equally to twice the penalty it seems that some of the bite could be taken out of these Feats.
Sorry, you've already lost me. This was the case of Power Attack back in 3.x, adn ti was such a time waster at the table. Most common was people trying to work out math to maximize their DPR. "Hey, we hit on AC 18 and missed on an 16, right. So if it's that the case, then I should use ...". The less common was the person who counts up his advantages/disadvantages every roll, and if they can't make a handy chart of what it will be it takes forever.
This may seem like an extreme reaction, but it really got my goat back then. I never again want lots of math options that need to be considered before every attack. A big/obvious one like -5 or not is okay, and non-math option that add interest and flexibility are great. But nothing this fiddly.
Cleanest solution for SS & GWM I've seen is adding "once per round" to the -5/+10 part. Then it can be a decent bonus like a feat shoudl give without being overwhelming on multi-attack characters, and it makes them interesting for single attack characters as well.