Rotom-Wash looks like your man. It has few weaknesses, access to a lot of support moves, Levitate, some strong attacks, and can sponge some hits while hitting decently hard back.
Rotom-W @ Leftovers
EVs: 252 HP / 144 SAtk / 108 SDef
- Hydro Pump
- Volt Switch
- Pain Split
Hydro Pump is your main STAB, and with it's high base power, it can put a hurt on a lot of Pokemon when in the rain or super effective, and it deals a decent amount of damage when neutral. Volt Switch is for scouting, gets STAB, and is all around a great move. Pain Split is Rotom's only form if recovery, and it works pretty well for walls and what not that can continually recover their HP. Will-O-Wisp cripples opposing physical sweepers, and gives a great boost to Rotom's physical bulk.
Reuniclus could also be the one you are looking for. Reuniclus has a huge SAtk stat, and with Calm Mind and Defense EVs, it is a bear to take down. It has weaknesses to Dark and Ghost types, but after a few Calm Minds, any special moves won't be doing much to you and you can take physical moves pretty well, even lower powered or non-STAB Dark type moves. With Magic Gaurd, Reuniclus can't have it's HP worn down by Poison, Weather, Burns, Leech Seed, etc. This means that the only way for the enemy to deal damage to you is to attack you directly.
Reuniclus @ Leftovers
Trait: Magic Gaurd
EVs: 252 HP / 252 Def / 4 SDef
- Calm Mind
- Focus Blast
- Shadow Ball
Calm Mind raises your SAtk and SDef, making you very hard to hit from the special side and raising your SAtk to very dangerous levels. Recover heals off any damage you may have taken setting up your Calm Minds and sweeping. Shadow Ball and Focus Blast are somewhat dissappointing as neither of them get STAB, and Focus Blast has poor accuracy. However, together, they have perfect neutral coverage, and when you can shrug off a hit from a plane, you can afford to have a miss every now and then.