I know they've got different terms for it, like netorare is the one from the perspective of the cuck, netori is the perspective of the bull, but what's the one for the perspective of the one being taken?
Perspective is only part of it and not required. Assuming standard genders, Mc <-> F <-(>) M(MMMM)
Netorare - Designed to evoke feelings of jealousy in the player, usually male MC perspective and heavy focus on original relationship.
Netori - Designed to enjoy watching the male MC get cucked, usually other males or female perspective.
Netorase - Male MC wants to get cucked. Can be a combination of both feelings above, or its own weird thing.
Reverse NTR would be about the opposite of Netorase. Designed to evoke a feeling of validation and desirability in the player. This can happen if its women pursuing the man for instance. Reverse NTR is essentially either a harem game or a love/lust triangle, favoring the guy.