My sun, my existence,
Shines down from heavens above.
It remains there with persistence,
Radiating peace, replacement of the dove.

lovely metaphors and great imagery... the last line is quite intersting... "replacement of the dove" - very deep

It sprays light onto the world,
Showing only the truest kindness.
Flying high with wings unfurled,
So beautiful, it can cure blindness.

Again, the imagery is astonishing... It reminds me of an angel, flying through the sky...

However, my sun does have its flaws:
Materialistic, comparing its light.
Often forgetting its sole cause,
Struggling through, using all its might.

intersting stanza... by using the metaphors of sun and light, we are supposed to believe that it is flawless... yet it does have flaws, like everything else in the world...

My family, my existence,
Crumbles down to the floor below.
It remains there, moving no distance,
Feeding on happiness, suffocating on woe.

The ending left me a little bit confused... I'm not quite sure how to interpretate it... the last line is very clear but the lines before lost me... you mean that you awoke to reality? that your existence takes you away from it?
are you talking about a heart, perhaps?

i ask myself why you used the title "supermassive black hole"... sun and black holes are completely different... was the title perhaps because of a muse influence in your poem? ;)

it is quite a good poem and flows wonderfully... yet i still ask myself what you meant in the ending...

*keep on*
isabel