Corporal Rivera was a Marine who served on Makin. He was seen when Miller did not follow Sullivan and Roebuck but instead went on the platform with Denny, Snider, and Slayback at the beginning. Near the end of the platform the player can see a Japanese soldier and a Marine fighting. If the player takes the right with Sullivan and Roebuck, Rivera would die. But taking the left gives the player a chance to kill the Japanese soldier. Rivera will try to find cover but can be killed while doing this. If he lives then he will be with the others whom are fighting the MG nest. After that and the Banzai attack then he will die with Rooker and Lozano at the second gunfight.
Strangely, if Rivera and Lozano live through the MG nest then Denny will die for no reason like Ryan would. Rivera held a Thompson. Also if Lozano and/or Rivera live (it can be both or only one of the two) Rooker will die at the 2nd gunfight by being shot instead of the ambush where he is stabbed.