Good at clearing out cramped areas with boost+ulti.
Roadhog needs a damn immortan joe skin. And did they nerf his shotgun? Dont recall getting a single instant kill from hook+full blast tonight.
I got a number of them on Roadhog, really all depends on who you hook/shotgun.
Tracer, McCree, and Reaper are pretty much hook, shotgun dead.
Widow, Hanzo, Genji, Soldier 76, Bastion and Junkrat have a bit more health and you'll need a hook, shotgun x 2 or melee. Most of those characters will run though when after you hook/shotgun them so if you don't hit them with melee, you can usually just shotgun them a 2nd time. Soldier 76 can be a bit harder if he drops down his healing pod.
The support are just a bit harder except for Lucio who is a freaking pain in the but. Zen is the easiest of the supports followed by Mercy and then Symmetra (because of her mini turrets). Lucio, unless at like half health, will require team support to usually kill so pull him in and let your team kill him.
Tanks are all team kills, if you can get behind Reinhardt and hook him it's great. Hook Winston outside his bubble, D. Va I tend to hook, shotgun and then jump over her as most people will just stand their trying to shoot the big fat tank.
I try not to fight Torb/Mei as they are pretty much the counters to Roadhog.
Also if you don't know you can juggle people with your ultimate as well as knock people off areas to die. I love doing this, especially to Reinhardt even when he has his shield up. Just walk into him past his shield and juggle away.