Ah. That’s different than “really bright from certain camera angles”, that’s “not being affected by lighting.” Youre using an unlit shader, which by definition is not affected by lighting. Unfortunately you have a secondary issue which is Unity doesn’t support shadow casting on transparent materials, so particles that are lit, and are in a dark area due to the light being shadowed will still be bright. There’s no easy solution to this since Unity explicitly does not support it.
See the now 10 year long thread on transparent objects not receiving shadows …
The hack work arounds are:
Render your own shadow maps, or copy the built in ones using command buffers and compute buffers, and manually pass them to custom particle shaders.
Use baked lighting and light probe proxy volumes and sample all lighting for particles from that, again using custom particle shaders.
Raycast from the particle system to the light to see if it should be considered in shadow and change the particle system’s start color.
Use hard edged or dithered alpha tested particles, which really can receive shadows.
Or less hacky would be to move to the new LW or HD pipelines, both of which support lit and shadowed transparencies, but you’ll likely still need custom particle shaders since neither really have good shaders for this yet.