>>33755389body language and cry. gf did a good job of conveying its emotions considering all the hurdles necrozma's fucked up anatomy provides.
best example is in pokemon refresh when you anger it and it curls up and just seethes - it even points its horns at you and sticks its knees out to look spikier and more threatening.
it's kind of hard to explain, better if you just watch:
https://youtu.be/JKltIYMP43E?t=37but to be frank with you, i think in its current state it is only very rarely happy, or never happy at all which is pretty fucking sad.