Whenever people claim that Paul taught something different than Jesus, I find myself wondering how closely they have read Paul's letters. Of all Jesus' moral teachings, probably the most unique is this: that the most important of all God's laws is the command that we love. The most important of all the laws and command God ever gave, Jesus taught us, is to love the LORD our God with all our heart, soul, mind, and strength; and the second most important is like it: to love our neighbor as ourselves. The main moral teaching of Jesus is developed better and more fully by Paul than by anyone else in the whole of the Bible.
Consider 1 Corinthians chapter 13. Here Paul devotes an entire chapter to love: how love is better than knowledge and wisdom and understanding; how even acts of charity are empty and meaningless without love, how even martyrdom itself is meaningless without love, that if we are martyred but do not love then "we gain nothing". Here Paul reminds us that if we speak even the most beautiful words of the most beautiful language with the most beautiful meanings -- but do not love, those who listen to us only hear an unpleasant noise like a gong or a cymbal.
Consider Paul's letter to the Romans, again chapter 13. Here Paul reviews from the standpoint of the law code of the Torah: that the law is fulfilled when we love each other. "Love does no harm to its neighbor, therefore love is the fulfillment of the law."
Again in Galatians 5:13-14, Paul expounds on love as the fulfillment of the law, and shows that the Christian fulfills the law by serving each other in love. "For all the Law is fulfilled in one saying: 'Love your neighbor as yourself.'"
As much as I find Peter's and John's writings to be admirable in their own right, and as much as they also proclaim Jesus Christ both in what he did and what he taught, still Paul is the one who proclaims Jesus' teaching of love the most.