Tyranitar/Hippowdown- For obvious reasons, perma-sand is needed for Excadrill, Tyranitar also takes fire atacks like a pro.
Gliscor/Landorus are pretty effective against fight pokes who can be deadly for the mole and they can also kill opposite Excadrill.
Garchomp- Resistant to fire and because he is very strong and one of the top sand sweepers.
Mamoswine- Very underrated pokemon but can kill Landorus and Gliscor who are top counters for Exca.
Heatran- Can absorb fire atacks.
Reuniclus- Good fighting pokemon counter and doesn't fear being burned.
Ferrothorn- Arguably the best rain team counter in the game can also take water atacks directed to the mole with ease.
Counters: Scarf Politoed and Ninetales can come into a swords dance or after something was killed, change the weather and KO the mole with their STAB atacks, Gliscor is the best counter he can take anything the mole throws at him and KO with STAB EQ, Landorus is at the same boat (and both can take advantage from the sandstorm) but needs to watch out for +2 returns that can KO him, Ballon Heatran can come into an EQ or a Swords Dance and kill the mole with a Fire STAB (or even Earth Power which can surprise an opposite Heatran who wants to absorb the fire atack), Bronzong takes little from Excadrill most used atacks but can't do much against the mole unless it is carrying Earthquake, Skarmory can also take on mole atacks and thrown as much Spikes as he wants before whirlwinding the mole away, Scarf Ditto can revenge non-ballon variants (though Scarf Ditto can revenge almost anything anyway), Fighting pokemons with priority atacks can kill the mole if it was prior damaged (I think Techniloom can even 1HKO an Excadrill with no HP or defense investments with his mach punch), Prankster Sableye can burn him.
Swords Dance Sweeper 252 atk/252 spe adamant
Item Baloon/Life orb
Standard Excadrill set, Earthquake has STAB and is ridiculously strong, Swords Dance turns the mole high atack into a huge atack, Rock Slide for flyers and the last option depending on what to kill X-Scissor hits some Grass Pokemons for SE damage, Return has no super effective hit but has more base power and Rapid Spin can clear entry hazards, item choice depends on the user Baloon makes him temporaly immune to earth atacks, while Life orb makes the mole hit harder.
Choice Band Sweeper Same EVS and nature as the above
Item: Choice Band
Basically the same set as the Swords Dance Sweeper with the diference it doesn't need to setup to break things and with the disadvantage of not being able to switch between atacks.
Special atacks- Should never be used. EVER. Even hidden power ice which could surprise a Gliscor is not worth it.
Choice Scarf- Can be good if you want to use the mole without sandstorm or if you want to use Sand Force.
Substitute- Can be interesting to protect the mole from status ailments and with HP investment his substitutes won't be broken by Seismic Toss, though he doesn't fear Blissey at all.
Toxic- Is an atack other pokes can use much better than him.
Hone Claws- An alternative to Swords Dance but it is worse since Earthquake is already base 100 accuracy.
Brick Break- can hit some ballon metals, but X-Scissor and Return are better options as atacking moves.
Poison Jab- A worse X-Scissor, Poison has terrible coverage.
Swagger- Maybe in a gimmick set with substitute...
Shadow Claw- Can hit ghosts but a SE Shadow Claw is weaker than a neutral Earthquake so it is meh at best.