My favorite controller was Imperious Rex, an ill/rad. (And yes, I created him in 2004, I imagine long before the Imperious Task Force came about)
As you can imagine, I got the name from the words Sub Mariner would exclaim preceeding certain battles.
I also got the name Ukase Rex from the words Doc Doom used as a pass code to get Ultron 5 to do his bidding in Marvel's "The Secret Wars" comic series. Absolutely loved that series.
I also had an earth/rad, and an earth/kin, a grav/kin, a plant/rad, an ice/emp and I forget how many others. I never did try */dark, but hope to do so. In my limited experience - for me - the ill/rad was the "best". With perma-pa, I could solo monsters - not defeat them, but hold my own. Never could get the dps high enough to get them, not without a heavy or several other temp pets. But, AVs, elites - they were dealt with easily enough. It took concentration, making sure I got the PA placement reticle in position fast enough to keep me from getting the aggro. Other than that, it didn't really matter. PvP - even without PvP ios, or a PvP build, he was pretty solid.
All that being said, there probably isn't a "best Controller". Maybe a "best controller for your playstyle" would be more precise. And, I think to answer that, you'll have to play them all, lol.
