Jesus is an Adam because he was made like us in every respect, apart from sin, and is the head of a new humanity. He is second because no man between Adam and Christ entered the world without sin. He is second also to remind us that he entered the world without sin himself. He is also second to remind us that he entered a fallen world, not the pristine world of the first Adam. Christ is last because there is not, and need not be, any like him who followed after him, since he reverses what Adam did in his sin and also accomplishes for us what Adam failed to do.
— Sinclair Ferguson