Normally gods bestow boons to others. It is very unlikely that somebody else bestows boon on them. Who can be more powerful than them to be able to bestow boons on them? It is not like that Brahmaa, Vishnu and Shiv always grant boons. Sometimes they also get boons from others. Today we will talk about the boons granted to Vishnu, and let us see who are such who could grant boons to Him --
Boon Granted by Madhu and Kaitabh
Madhu and Kaitabh were two great Asur who were born from Vishnu's earwax. In the beginning there was only water and on that water there was Vishnu lying on His Shesh Shayyaa. Then appeared Brahmaa Jee from His navel After a while Brahmaa Jee started his creation. Earwax started flowing from Vishnu's ears and two great Asur were born from it - Madhu and Kaitabh. Since Brahmaa Jee were creating the world at that time so they were born from Rajo Gun and Tamo Gun.
They did Tapasyaa for 1,000s of years and got the boon of Ichchhaa Mrityu from Devee - when they want they will die at that time only. With this boon they started troubling the universe. Once they saw Brahmaa Jee, they asked him who was he and from where he had come? They came to know that he was born from Vishnu, so they came to Vishnu and started fighting with Him. The Asur were very powerful. the fight continued for 5,000 years. Vishnu knew that He was weaker, and the Asur also knew that they were more powerful than Vishnu, so they said to Vishnu proudly - "Surrender to us that you are our servant." Vishnu said - "We have been fighting for 5,000 years, but I am only a single and you are two. You have already taken rest in between, now let me take some rest, then I will fight. " So they left Vishnu alone for rest.
Vishnu remembered the boon granted by Devee to them. It was because of that boon that they were not feeling tiredness, so He decided to seek help from Devee too. Devee said - "Go and fight with them, and I will delude them with my sight." So Vishnu went to fight with them. Devee deluded them with her sight. At the same time Vishnu said to them - "I admire you, you are very brave, ask for a boon." They were very proud of their might, so they said - "We are not beggars, instead you ask us for any boon you wish for. We can give you whatever you want." Vishnu wanted the same, so He said - "If you are pleased with me then grant me this boon that you should be killed by me now." They said - "We are cheated." Since at that time the whole Prithvi was covered with water, they said - "Then kill us where there is no water on Prithvi."
Immediately Vishnu expanded His thighs, showed them the vast Prithvi on the waters. He asked them to keep their heads on His thighs. They also expanded their bodies to 10,000 Yojan. Vishnu also expanded His thighs twice the size of their bodies. Seeing this they kept their heads on His thighs. Vishnu immediately cut their necks with His Chakra. That is how those Asur granted the boon to Vishnu to kill themselves.
Boon Granted by Gajmukhaasur
Gajmukhaasur was a very powerful Daitya. Once he did a severe Tap for Shiv Jee and asked for a boon that he should live in his belly. As Shiv had granted this boon to him, he had to comply with tthe boon. he started living in his belly. Now some time passed and Paarvatee Jee did not see Shiv Jee so she went to Vishnu and asked His help. Vishnu took Shiv's Nandee Bull, assumed the form of a flute player and started playing flute. Nandee started dancing on His tune. Now they started going around playing flute and dancing.
Once they came to Gajmukhaasur's residence, many of the servants of Gajmukhaasur started coming there to see the show. Some admired the show to Gajmukhaasur also, so he also came out to see it. Vishnu understood that this Gajmukhaasur is the one who has hidden Shiv. So they played the flute and danced very well. Gajmukhaasur got very pleased hearing the flute and seeing the dance of a bull. He asked Vishnu to ask for a boon from him. Vishnu asked him - "Are you serious? You will grant me the boon?" The Asur said - "Yes, I will grant you the boon, ask me anything, I will give it to you." Vishnu said - "Then you release Shiv. You have hidden him, I want him back." The Asur now had to give Shiv back. As Shiv came bursting out of his belly, the Asur died in this process.
These are the only two boons Vishnu got from Asur.