Conversation so far:
Who was Innocent IV?
A new pope, Innocent IV, was elected on 25 June 1243.
Was Innocent IV viewed as a good pope?
The Emperor was initially happy with his election. Innocent, however, was to become his fiercest enemy.
Why were the Emperor and Pope Innocent enemies?
Negotiations began in the summer of 1243, but the situation changed as Viterbo rebelled, instigated by the intriguing local cardinal Ranieri Capocci.
Who prevailed in the rebellion of Viterbo?
Innocent convinced the rebels to sign a peace but, after Frederick withdrew his garrison, Ranieri had them slaughtered on 13 November.
Pope Innocent was happy with this solution to the rebellion of Viterbo?
The new Pope was a master diplomat, and Frederick signed a peace treaty, which was soon broken.
Was Pope Innocent and Frederick II, Holy Roman Emperor's feud ever resolved satisfactorily?
Between February and March 1247 Frederick settled the situation in Italy by means of the diet of Terni, naming his relatives or friends as vicars of the various lands.

Question: What else was significant about Innocent IV?
Self-contained rewrite: What else was significant about Innocent IV's relationship with Frederick II besides feuding, inciting a rebellion, brokering a peace treaty, and breaking this same treaty?