Hello everyone and welcome to my 125th analysis, this time featuring Warthak the Skullcrusher.
Overview: Despite his Control Immunity and largely shared movesets between his two other forms, Skullcrusher fails to be nearly as effective as them simply because he lacks the Stun and Daze they offer, plus his moves have lower Base Powers, not to mention his noticeably lower Base Stats. Quicksands is one of the most offensively effective Tortures, but even it can't save Skullcrusher. Compared to other attackers, however, Skullcrusher has a good damage output that should not be overlooked.

Builds:
Monsters that have access to Group 4 skills will have a slightly different build path. I will list the most viable builds for each Rank since some moves in Group 4 are pivotal to some sets' success. The monster's role will likely remain the same, however, so this won't be exhaustingly long as I won't repeat the same things.

Rank 0:
Moves:
-Skullcrusher Stroke
-Dawson Ghost
-Restored Petroglyph
-Single-Handed Skullcrusher
Runes: 2 Strength 1 Speed
Mutant Rune options: Strength&Life, Speed&Life
Relics: Armors and Swords

Build Explanation:
Skullcrusher Stroke is Skullcrusher's weapon versus CD activators, having 55 Base Power and applying Quicksands to its target. Dawson Ghost is a Base 60 skill that also comes with buff removal and Damage Reduction. Restored Petroglyph is Warthak's best AOE move at this point, having 40 Base Power and the treasured 100 Accuracy, and while the Shield removal is largely not going to be useful, it can sometimes come in handy. The last slot goes to Single-Handed Skullcrusher, Skullcrusher's most powerful attack at this point that also applies Quicksands.
2 Strength 1 Speed with Life Mutations are the standard for attackers.

Rank 1: Skullcrusher learns "Marikana Wraith" at this level, a Base 40 unresisted AOE that removes buffs from all enemies before dealing damage, then applies Damage Reduction to them.
Moves:
-Skullcrusher Stroke
-Dawson Ghost
-Marikana Wraith
-Single-Handed Skullcrusher
Runes and Mutant Runes are the same as given above.

Build Explanation:
Marikana Wraith is infinitely better than Restored Petroglyph, because it removes buffs and removes them before dealing damage as well, which includes Shields. It is also unresisted and softens up enemies with Damage Reduction. Warthak can use this to target enemies that are hiding behind protection like Phobic Shields and Evasion.

Rank 2: Skullcrusher learns "Perfect Petroglyph" at this level, a Base 45 Earth AOE with 100 Accuracy that applies Shield Blocker to all enemies.
Moves:
-Skullcrusher Stroke/Perfect Petroglyph
-Dawson Ghost/Perfect Petroglyph
-Marikana Wraith
-Single-Handed Skullcrusher
Runes and Mutant Runes are the same as given above.

Build Explanation:
Perfect Petroglyph is Warthak's most powerful AOE in terms of damage, and it has 100 Accuracy to boot. It can be used over Dawson Ghost, but you may still prefer Dawson Ghost's ability to break through protection effects. It can also be preferred over Skullcrusher Stroke, since this Stroke move isn't nearly as impressive as Sunbringer or Mountainsplitter's.

Rank 3: Skullcrusher learns "Two-Handed Skullcrusher" at this level, a Base 75 Earth move that removes the target's Shield and applies Quicksands to it.
Moves:
-Skullcrusher Stroke/Perfect Petroglyph/Single-Handed Skullcrusher
-Dawson Ghost/Perfect Petroglyph/Single-Handed Skullcrusher
-Marikana Wraith
-Two-Handed Skullcrusher
Runes and Mutant Runes are the same as given above.

Build Explanation:
Two-Handed Skullcrusher is one of the most powerful attacks in the game, and it wil deal great damage to anything it targets, especially with the Quicksands and Shield removal it offers. It replaces Single-Handed Skullcrusher in the last slot, though said move can still be used in the first or second slots.

Teammate Options: For Teammate options, check out this article.

Countering Warthak the Skullcrusher: For Counter options, check out this article.