ANY army can win with good tactics and focus
I'd suggest Daemons of Chaos, they're as far as you can possibly get compared to...Well ANY army in
40k. No deployment ever

and the bonus is you can use the army in conjunction with Chaos Space Marines (I collect both armies, and damn Apocalypse is fun with my traitor guard, Daemons and Chaos marines all gracing my army roster.)
Just know that Daemons has got its competitive builds and I find its generally good, but expect to play at a slight disadvantage seeing as every marine player either has nullvoid, and the new
GK codex coming out will most likely make me pack in my Daemons until the next flavour of the month comes out.