The Druddigon set i love the most is the Sheer Force all out attacking set with Outrage / Fire Punch / Thunderpunch / Sucker Punch, max Atk and HP (or a few Speed evs to speed creep) with an Adamant nature and LO as the item. This thing is simply amazing! It can 2hko everything in RU (except support Aggron, which is stupid), have strong priority, great bulk and resistances, meaning many switch in opportunities, and 2 very strong moves that don't lock you and don't have LO recoil.
Fire Punch is an awesome move to spam as not many Grass, Fire, Water and Rock types would switch into Druddigon, and it hits like a truck, 2hkoing most things that don't resist it in RU. Outrage is Outrage and has awesome neutral coverage and is your stronger move, and the fuck you all button when all Steel types are gone, and Sucker Punch is awesome and strong priority. Btw standard Nidoqueen is always 2hkoed by Fire Punch + Sucker Punch, and Druddigon is never ohkoed by any of Nidoqueen's move (Ice Beam does 95% max, so at worst you will die after killing it with Sucker Punch from LO recoil. Btw Ice Beam is rare). Now about the odd move, Thunderpunch. This move is what enables Druddigon to beat the infamous Steelix + Slowking as well as the TangKing combo. Without Tpunch, Slowking could make you lock yourself into Outrage if you wanted to kill it, which meant that Steelix would wall you, and Slowking could status you as he can take one Outrage from full life. But with Tpunch no more Slowking. Slowking takes ~80% from Tpunch, which is a ohko after Fire Punch, and Steelix is 2hkoed from Fire Punch, so with proper prediction you can beat the core. Same for TanKing, where Slowking would again force you to lock yourself into Outrage, while Tangrowth could tank 2 Outrages and put you to sleep. With T-punch you are also able to ohko many water and flying types without locking yourself into Outrage such as Aerodactyl, Kabutops, Feraligatr, Moltres, Crawdant and Sigilyph. For this reason this set is an excellent lead as it can beat many common leads such as Aero and Nidoqueen with the combo of Fire Punch / Thunderpunch and Sucker Punch. Without Tpunch, Aero would be able to both set up SR, and deal great damage to you with Stone Edge, as you would have to lock yourself into Outrage in order to kill it.