Wall Street thinks these struggling stocks are undervalued, and certain analysts expect monster gains in the next year.Shares of The Trade Desk (TTD 5.61%) and MercadoLibre (MELI +2.49%) have declined 71% and 24%, respectively, from their record highs. But Wall Street analysts generally think the stocks are undervalued, and some anticipate substantial gains in the next year.Among 42 analysts, The Trade Desk has a median target price of $60 per share, implying 53% upside from the current share price of $39. ...