Defeated the Sandworm (Boss?) on Hard several times, but no achievement. Searching for solutions online has been fruitless.

Originally posted by GenieonWork

First of all, only for the person dealing the last blow it will count as having killed it. Before it became a Steam achievement, it was already an in-game achievement. We've killed numerous sandworms, black wolves, scorpions etc, but it has always been the case that the player dealing the death blow was the one who got the in-game achievement. If your mounts killed the Sandworm, that's a possible reason why you as a player did not get the achievement.

Another thing: When you go in solo (without other players, without mounts) and you use for example fire arrows and the last tick of health is taken away by fire, it does not count for you as player; it's the fire that dealt the last blow. Keep that in mind when soloing the Sandworm.

Lucky for you the Sandworm is the easiest world boss to take down, once you know it's attack pattern. How I personally deal with sandworms (I kill them just for fun, since I've already got the achievement and they're very easy to avoid): Go in close. If you stay within a couple of feet, it's never going to spit (although to play safe you might want to take a green pill, just in case). It follows a very easy attack pattern. You go in close and hit him with your knife. It's going to do a spinning attack which will knock you a fair distance away, so pull back like three feet. After his spinning attack, go in again and hit him with your knife again. It's going to do a double spinning attack, so pull back a couple of feet again. Just rinse and repeat. Single spinning attack, double spinning attack, single, double. Once you know how many times you can hit him between attacks, it becomes very easy (for me it's like seven hits). Again, keep close so he doesn't spit. Occasionally he'll lunch out trying to hit you, but you'll learn to recognize when this is coming by the way he moves.

It will wear out your knife, so you might want to carry an extra knife just in case.

The advantage of this attack is, every time you hit him, he drops a scale. Since it takes quite a few knife hits to kill him, you'll end up with a lot of scales (100+ is no exception).