If you use Trick Room, you could pull it off.
The best special set (assuming Trick Room is up) I guess would be:
Cacturne @ Life Orb
Ability: Water Absorb
EVs: 252 Sp. Atk, 252 HP, 4 Def/ Atk
Nature: Modest/ Quiet
-Nasty Plot
-Giga Drain
-Dark Pulse
-Focus Blast/ HP Ice/ HP Fire/ Sucker Punch
On a purely special set, you forfeit Sucker Punch, which is really crucial to Cacturne doing any damage, because it's so slow. Cacture can set up one Swords Dance without being KO'd, but the chances are unlikely; it only works with a physical set without the help of Trick Room because of Sucker Punch's priority. Additionally, Cacturne needs to rely on a low accuracy move like Focus Blast for coverage, when it can have Drain Punch + Swords Dance when running a physical set. If you really want to run a special set, I would still recommend Sucker Punch, simply because that move does incredibly well for Cacturne's slow speed. Cacturne would have to run a mixed set, but I guess you can just forfeit speed for its nature, since it's so slow anyway that it won't really matter. If you're running Sucker Punch, Trick Room isn't needed but will be massively beneficial.
Depending on if you run Sucker Punch or not, give it 4 Def or 4 Atk Evs.
I guess you could just Scarf it. At max speed, it will be 229, which means its speed will be 343.5 with Scarf boost, which is pretty poor for a Scarf'd Pokemon, but if that's what you want then so be it.
