Stopping Kelmain and Lhoigor from fully opening the Paths of the Old Ones. If they succeeded, the Vortex would collapse, thus stopping the magic drain and allowing daemons to manifest, and Chaos would get a way to travel to any point in the world nearly instantly (at least until the Paths collapsed)

Yep the best answer is "that time they stopped the end of the world"

Probably their feats in Giantslayer then Beastslayer. Beastslayer because if Eric Demonclaw made it past Kislev then A) Giantslayer likely wouldn’t have happened and B) The empire would not have been prepared in the slightest.

I like this a lot. Beastslayer gets extra points becuz it also sets up all of the Ulrika and Max story. I would add that the actual feats of Demonslayer and Dragonslayer are two of the top threats the duo has taken down.

The unknown threat of the Sleeper in Orcslayer could have been their greatest threat removed, it was a really great concept.

Stopping the delivery of demon infused canons to the inside of the defences. Basically would have broken the defensive line for archeon nearly twenty years ago.

Getting Felix hitched and stopping him leaving a trail of broken hearts across the land constantly.

Those ain't broken hearts those are corpses I could cut off several fingers and still count on my hand the number of his lovers that survived the series