Complex sentence: S.H.I.E.L.D. surgeons were actually able to bring Coulson back to life days after he had been killed, but altered some of his memories to make him believe that he was revived in Tahiti in order to erase the trauma he experienced during the procedures.
Split into simpler sentences: S.H.I.E.L.D. surgeons were actually able to bring Coulson back to life days after he had been killed. During the process, they altered some of his memories to make him believe that he was revived in Tahiti, in order to erase the trauma he experienced during the procedures.