Let's take a look at four "toxic stocks" to sell, and when to sell them. A descending triangle pattern makes AES Corp. ( AES) a sell below $11. Michaels Cos. ( MIK) has been stuck in a textbook downtrend since last summer. Sell the next resistance failure. Costco's ( COST) trend line break following Q2 earnings is a sell signal. A classic head-and-shoulders top in Tesla ( TSLA) triggers if shares violate $240 support.