What shout did Ulfric use to kill the high king?
Is there like a mod or somthing that you can use to get the shout?

It's quite possible that he just used Unrelenting Force to knock the High King to the ground, then stabbed him with his sword. I don't think that he literally killed the king with his shout.

This. The claims that he "shouted Torygg apart" are Imperial BS. He used unrelenting shout which is the only shout he knows. He staggered Torygg then killed him, not shouted him apart. Next time don't believe Imperial propaganda

Actually, if you bring up the subject with Ulfric, he confirms that this is exactly what he did.

If memory serves me correct I believe Elisif will also confirm that Ulfric did challenge Torig in the old ways and then shouted him off balance and killed him. Torig's honour left him no choice but to except Ulfric's challenge even thou everyone knew he could never win. This is why the Empire calls it murder while the Stormcloaks calls it fair combat.

I think I remember asking him about it and he said something about "True, I did use a shout. But it was my sword piercing his heart that killed him."
Thanks for jogging my memory lol.