By Chuck Mikolajczak (Reuters) -The S&P 500 fell to its lowest level in almost two years on Tuesday on worries about super aggressive Federal Reserve policy tightening, trading under its June trough and leaving investors appraising how much further stocks would have to fall before stabilizing. Stocks have been under pressure since late August after comments and aggressive actions by the U.S. Federal Reserve signaled the central bank’s top priority is to stamp out high inflation even at the risk of putting the economy into a recession. The S&P 500 was last down 0.6% at 3,632. After the benchmar…