Natasha Romanoff X Male Oc/Reader

Oc is Thor and Loki's older brother

Oc is Thor and Loki's older brother. 

He is the god of animals and nature. His powers let him transform into any animal that has ever existed, transform into giant improved versions of animals, Talk to animals, Control Nature , Fly and he has enhanced strength, Speed, stamina and senses. 

He has a horrible relationship with Odin so he faked his death and convinced Heimdall to keep the secret of him being alive.

He arrives on earth in the woods/jungle that is isolated from people. 

SHEILD gets strange readings but they weren't able to track the readings (Heimdall intervied) 

Years pass and Oc has lived in the Woods/Jungle until he notices that all the animals are acting weird. And after talking to them he discovers that they can sense something bad is happening, he flies to were the animals says it will happen and he arrives just in time to see the portal open.

He starts saving everyone he can but when he sees it's Loki his younger brother attacking innocent people he becomes enraged and transformed into a giant Gorilla (smaller than Kong)and attacks the giant space worms. 

The avengers are in shock and Thor recognised him immediately and tells them that it's his older brother that he though was dead. 

Oc sees a building about to crush people and he gets there just in time sheilding them with his body. 

He then transformed into a giant cheetah (flash level speed) and speeds around the city picking up people and speeding them away.