I will have to go with the 3.5 Dragonborn and the Raptoran as the worst two races in D&D. Does anyone here remember when WoTC introduced everyone to Level Adjustments (LAs) and Effective Character Levels (ECLs) in their
Savage Species book? This book had rules on how to play powerful beings such as Minotaurs and Giants as player characters. It did this by looking at every trait in a monster's stat box and assigning each of them a LA, which could then be totaled up to determine that being's ECL. As a result, beings such as Minotaurs had an ECL of 8, which meant that they could only be played when everyone else in the party was 8th level as well. You couldn't play one as is at 1st level because they were simply too powerful. You could, however, play one if you took up a Minotaur class and then later multiclassed into the character class you wanted them to have.
I don't know about the rest of you, but I found the whole LA/ECL to be pretty discouraging. Which apparently was WoTC's intent all along.

I can't remember which 4e book spilled the beans on WoTC's intent to discourage the players from playing Giants, Hags, etc. But I do remember reading that WoTC was worried about the fans 'desire' to play something powerful would render the standard races obsolete. There was also that nagging balance issue.
Anyway, the very rules that were meant to discourage players from playing something powerful also proved to be something of a hindrance to any attempt on WoTC's part to create new player character races.

How else to explain the staggered approach they used for each of the paths a 3.5 Dragonborn could take for their breath weapon, their senses and their ability to fly? Ditto for the staggered approach in the Raptorans' ability to fly.
I am glad that the 5e Dragonborn are slightly better than their 3.5 counterparts. I say slightly because they're still being 'confused' for Half-Dragons.

Not really.
