NPC becomes see-through in third person while using the Leawind's Third Person mod and shaders such as complementary reimagined/unbound.

Thanks for the report. According Leawind's Third Person mod description, this is expected. See:

Player Transparency: Player entity becomes semi-transparent when the camera is close or the crosshair is aimed at the player.

Most of the NPCs are using a player model, so I assume that the mod is false set the models to semi-transparent.
Please flag this issue with the Leawind's Third Person mod author.

Will do, thank you