Although part of the plot to kill and later enslave their brother Joseph, it is Reuben who advises the others not to kill Joseph, see Genesis 37:20-22, and who later points out that their troubles in Egypt were the consequence of the plot, see Genesis 42:22. Later he offers his own two sons as surety for the safety of Benjamin, see Genesis 42:37, in order to more quickly relieve the famine, an offer Jacob refuses. He is probably the wisest and most compassionate of the older brothers.
But as firstborn, Reuben should have been the leader of his brothers, and have taken responsibility for their collective actions, which he fails to do. His other failing is to commit incest with Bilhah, see Genesis 35:22, 49:3,4.