DERA ISMAIL KHAN, Pakistan — Pakistan's Taliban commander Baitullah Mehsud, who unleashed a fearsome campaign of suicide attacks and assassinations that made him the country's most-wanted man, was killed in a U.S. missile strike, an aide said Friday. The U.S. put a $5 million bounty on his head in March. Increasingly, American missiles fired by unmanned drones have focused on Mehsud-related targets. While his demise would be a major boost to Pakistani and U.S.