Without a doubt the widest chasm exists here. Evangelicals insist on the Biblical teaching of justification as an imputed act of God whereby the sinner is declared righteous. A sinner is saved by grace through faith alone through Christ alone. Catholics teach a system whereby righteousness is infused in the sinner. It is a system of grace plus works.
Little distinction is made between justification and sanctification in Catholic theology.
With the non-biblical teaching of purgatory there is always a second chance. Catholics see communion as an actual reenactment of the sacrifice of Christ. While all protestants do not agree, most see Christ as present at communion and the partaking of the elements as a memorial of His historical sacrifice on the Cross. The partaking of the elements is never seen as a means of Grace as in Catholic teaching. The priesthood of every believer is perhaps the second most important difference demarcated by the reformation.