I actually kinda feel bad for Duraludon. You can tell GameFreak put a lot of effort into making this pseudo-rival counterpart to Tyranitar, but it just falls short in too many departments to be considered competitively viable in the higher tiers. It has excellent defense and special attack, but is let down by poor special defense, HP, and base 85 speed with no means of boosting it further. The movepool also leaves a lot to be desired, and you would think a Pokemon that looks like a gun would at least have access to Ice Beam and Flamethrower, but no. Too frail on the special side to be truly defensive despite good defensive typing, too slow to be a reliable sweeper. This thing was supposed to be popular, but instead it just became a neglected mess of a Pokemon that didn't live up to its own ambitions. Honestly, I would rather use Aggron despite its 4x weakness to Ground and Fighting attacks.
Suicide Cannon
Ability: Light Metal
Item: Choice Specs/Choice Scarf
Nature: Timid (+Speed -Attack)
EVs: (HP 4) (Sp.Att. 252) (Speed 252)
Moves:
Draco Meteor
Flash Cannon/Steel Beam
Thunderbolt
Dark Pulse/Body Press
Set Details:
A straightforward choice set that tries to hit as hard as possible with what little you have. Draco Meteor has the high power, and the special attack drop can be remedied by a simple switch out after hopefully landing the knockout. Flash Cannon is your secondary STAB option that can be used consistently, though Steel Beam is worth a mention just to surprise your opponent with a move even stronger than Draco Meteor, but that 1/2 HP recoil is devastating and should always be in the back of your mind. Thunderbolt is your best special attack option against Steel types that block both of your STAB. Dark Pulse also serves the same purpose for general neutral coverage, but Body Press is also an option since it uses your high defense and not your attack stats, and though it doesn't get the Specs boost it is still your best option against Steel types overall.
I feel I should also mention its Gigantamax form as well since it is one of the few Pokemon that gets one. It's signature G-Max move Depletion basically serves as a Spite on top of an attacking move which lowers your opponent's PP of the last move it used by 2, which frankly pales in comparison to the Attack drop offered by Wyrmwind. If the PP drop was the same as Spite's (-4 PP) I could have seen some use for it to quickly drain your opponent's PP of their more powerful moves while keeping the offensive pressure, but that is not the case here, so regular D-Max is preferred.