What about Marcel Darius? Our signing him to a contract with $60m in guaranteed money in 2015 should rank right up there. He had 2 sacks that year. The next year he had a 4 game suspension for substance abuse, and had a whopping 3.5 sacks.
In Marcel's defense, we did get Wyatt Teller with the pick we got from Jax when we traded him. That worked out pretty well.