Lopez dislikes Simmons attitude seeing him as racist and as much of an idiot as the rest of the team, Despite this he is still willing to build machines for him and lends support during the confrontation with the Meta.
Lopez hates Grif simply because Sarge programmed him to. When Sarge orders him to execute Grif, Lopez is extremely grateful and happily complies. Considering Grif's nature, it is likely that Lopez hates him naturally.
Of all the members on Red team, Donut is perhaps the one Lopez hates the most, like Simmons and Grif, he finds him highly annoying due to his idoitic mood and his terrible attempts at speaking and translating Spanish
Lopez has little interaction with Church, the most showing he dislikes him due to being "constantly possessed and blown up".
Caboose is Lopez's rival for Shelia's heart and dislikes him for for it, but Lopez shows no contempt for Caboose for this reason.
When Lopez and Shelia first met, they instantly fell in love, having a brief, affectionate talk before Lopez is shooed off by Caboose.
Lopez has no interaction with Wash apart from being shot