Hanuman is Hindu mythology is considered as reincarnation of one of the mightiest Gods.
In Hindu mythology Hanuman is known as Pavan Putra, aka son of the sky.
He isn't actually reincarnation of Shiva, but could be argued. It isn't stated in any of the Vedas that Hanuman is avatar of Shiva tho.
And not every incarnation of Vishnu is above Hanuman either.
Parshurama is one of the avatars of Vishnu in Mahabharatta and he wasn't even the strongest human in Mahabharatta itself and top tiers of Mahabharatta like Karna, Arjuna, Bheeshma are all below Indrajeet much less ravana who are both ashuras.