Vishnu

Vishnu is the supreme godhead of Vaishnavism (Para Brahman or Nirguna Brahman) in puranas. He is called Swambhagwan in the Ramayana and Mahabharata. Vishnu is one of the three main gods in Hinduism and is the supreme being in the Vaishnava tradition and vishnu is a member of the Trimurti in Hinduism.
Vishnu is the god of preservation. This means that he protects the universe from being destroyed. It is believed that Vishnu holds the Earth and all living organisms. According to the Hindu religion, he has set foot and arrived on the Earth in nine forms called avatars, so far with one incarnation yet to come that is Kalki at the last to be Kali Yuga, to destroy evil. His most famous incarnations are Rama, Krishna, Parashurama, and Narasimha!
Vishnu holds a lotus, or Padma, the indestructible mace of Vishnu (Kaumodaki), a conch (Shankha), and the unstoppable disc of Vishnu (Sudarshana Chakra) in each of his four hands. He is known to take many disguises, but the three main forms of Vishnu are Mahavishnu Karanodakshayi Vishnu (Mahavishnu), Garbhodaksayi Vishnu, and Kshirodakashayi Vishnu, the other two are the expansions of Karanodakshayi Vishnu.
Avatars
There are 10 avatars of Vishnu (in the order they appeared):
Matsya (fish)
Kurma (turtle)
Varaha (boar)
Narasimha (half lion, half man)
Vamana (dwarf)
Parashurama (Fierce man/Hunter)
Rama (developed man/fighter)
Krishna
The diverse branches of the Hindu Tradition accept the ninth form of Vishnu as the following:
Jagannath (abstract form)
Budhha (enlightened man)
Kalki (future avatar, has not appeared yet)
Icons
Vishnu holds items in his four hands. He holds a conch in the upper left hand, which represents victory. He holds the Sudarshan Chakra in the upper right hand, which represents spiritual energy. In his lower left hand, a lotus (flower) represents peacefulness, and in his lower right hand, the Kaumodaki represents Vishnu's powers.
Temples of Vishnu (Mahavishnu)
The Kodlamane Shree Vishnumurthy Temple is dedicated to Vishnu and is the ancient Tirth Kshetra. There is no other place like this anywhere in Brahamanda.
Powers and abilities
Vishnu has omniverse manipulation, absolute manipulation, meta manipulation, and preservation. As the preserver, Vishnu can control anything and everything. The power to protect everything from anything is the reason he is also called the supreme protector of his devotees.
Absolute destruction: In the Vishnu purana, Vishnu is also described as the creator, destroyer, and preserver. As the destroyer, he can even destroy infinity or the omniverse.
Omniverse creation or absolute creation: As the creator in the Vishnu Purana, Vishnu has the power to create everything, even infinity and beyond. The power to have limitless power upon seeing the Supreme form of Vishnu. Arjuna describes him as having infinite prowess or power.
Omnipotence : Vishnu has the power to do absolutely everything, even creating something that is bigger than infinity itself. In chapter 11 of the Bhagavad Gita, Krishna/Vishnu shows Arjuna everything--all creation: time, space, past, present, future, the omniverse, fictional and real human beings, and more. It is beyond human imagination to actually comprehend it.
Omniscience: the power to have infinite wisdom experience and knowledge.
Omnipresent: The power to be everywhere at every time including beyond the omniverse in both past present and future. When Krishna/Vishnu shows his Supreme appearance, it is described being everywhere, yet people can't see it because they don't have the divine vision. Only Maharishis/sages, gods, Sanjaya, and Arjuna are able to see this Vishvarupa.
Formless: Vishnu's true form is described as formless, infinite, boundless, inapplicable, without shape and color, according to Vishnu Purana.
Absolute immortality: Chapter 1 of Vishnu purana describes Vishnu being boundlessly above the concept of death idea and life.
Absolute Transcendence/Being Above All Things: The Vishnu Purana also describes Vishnu as being above all descriptions such as logic, time, space, etc. He is an infinite dimensional being according to Vishnu Sahasranamam.