Almost every example of dangerous creatures that humans have hunted (in the given technological era) were hunted with spears or missile weapons (generally bows).
Despite what computer games might tell you weapons like swords, axes, maces etc. aren't much use because you need to get too close to use them.
If hunting a boar was dangerous and required a special spear you can be sure that hunting an elephant sized monster will also require a spear. Spears allow you to strike with reasonable force from far away, they can be used defensively so the animal runs on to it using its own momentum to drive the spear in, they are cheap and easy to make and also easy to learn to use.
Missile weapons like bows are also useful but it would depend on how thick the creature's hide is and how fast it is. If it's a lumbering giant you might be able to put enough arrows in it while staying at a safe distance to kill it, but a faster creature might get within attack range after only a few shots.