I'm not saying he's not scary, he is. But...Does he really deserve to lead the scariest characters in the DC Universe? I don't think so. He doesn't seem to truly understand and embody fear as much as he seems to use it like his dad's gun which he stole or something. If anything he's more deserving of a Orange Lantern ring. Here are some DC Characters much more deserving of the title of leader of the Yellow Lanterns.
1) Arkillo~He is more committed to his cause, often resorts to terrifying tactics of torture and murder to get what he wants, cannibalizes people and eats failed recruits. HOW IS HE NOT THE LEADER!!'
2) Scarecrow~...Do I even need to explain this?
3) Batman~Batman's entire training, combat and personality resolves around fear...More so then Sinestro.
4) Doomsday~He has pretty much the entire galaxy on their toes in fear and terror. His very name seems to invoke fear and anxiety.
5) Anti-Monitor~See Doomsday
6) Cyborg Superman~See Arkillo
Seriously, THIS guy is the face of fear in the universe? Come on!