I have tons of comics, but sadly, only a few X-Men: Onslaught series...if I remember right, though I have no clue how, it was more like Mags and Xavier somehow fused together, but Xavier being held prisoner on the guy's back.
I did see, but didn't get the chance to buy, a comic where Onslaught shows his full power-by flicking his right wrist, he reduced half (or so) of Manhatten to burning rubble.
*also note, I do have one comic where Nate of the "Age of Apocolysp" series (sp) shows the X-men who they where dealing with.
oddily enough, isn't it xavier? this onslaught anyway. well both technicly are xavier(there are two different onslaughts), but one needed the (unwanted!)help from magneto to exist. sorta. too many details, too little time. I will say this, the one you drew as far as I can tell looks more like the pure xavier version. on the otherhand, if this is purely fan-made and has no relation to THAT onslaught, kick ass, you fooled meh!(^-^) zawezome pic.