Allah does not forgive associating partners with Allah (Quran 4.48). What is the reaction of Brahman to associating partners with Brahman?

Allah is self-sufficient, separate from the Universe and transcendent, he is individual, unique and special and there is nothing like him. He created the universe and humans so that they could worship him.

I created the Jinn and humankind only that they might worship Me. (Quran 51:56)

So under these conditions, failure to fulfil our purpose of existence by worshipping Allah alone, we incur his wrath and disfavour and will be damned for eternity.

BRAHMAN himself has become the Universe and all in it, for his own pleasure and not that the creatures should acknowledge him or in any way show him gratitude or subjugation.

It is like an artist who creates a beautiful painting - for his own self-expression and delight - why would he want the painting to thank him for its creation or worship him?

The creation itself gives pleasure to the creator; the creation itself is gain to him. Brahman projected the Cosmos 14 billion years ago and humans emerged a mere 200,000 years ago - he was wrapped in delight and joy from its very inception and humans are a tiny pixel in this vastness of time-space.

Taittiriya Upaṇiṣad Bhrigu Vaḷḷi Anuvāka 6

ānando brahmeti vyajānāt | ānandāddhyeva khalv-imāni bhūtāni jāyante | ānandena jātāni jīvanti | ānandaṃ prayanty-abhi-saṃ-viśantīti ||

He realised that Brahman is Bliss (ānanda), for from bliss all these beings are born; by bliss, when born, they live; into bliss they enter at their demise.

So in short there is nothing lacking in Brahman which He/She/It requires or desires. Brahman is complete and perfect (pūrṇam), not separate from the creation and all the individual modalities of consciousness, so the question of “associating partners with Brahman” is naïve.