According to Sukhsagar, 24 incarnations of Lord Vishnu

Sukhsagar, a major scripture of Hinduism, describes twenty-four major incarnations of Lord Vishnu. These incarnations are assumed by Lord Vishnu for various crises of life and for protection. The stories of the twenty-four incarnations are found in the Bhagavad Purana, Vishnu Purana, and other Puranas. Following are the twenty-four major incarnations of Lord Vishnu:

Sanakadi Rishi : Lord incarnated in Kaumarsarga in the form of Brahmarishis named Sanak, Sanandan, Sanatan and Sanatkumar. This was his first incarnation.
Varahavatar: To bring the earth from the abyss, God incarnated in the form of Varaha and killed Hiranyaksha.
Narad Muni: Incarnated in the form of Narad ji to preach Sattvatantra to the sages, which is also called Narad Pancharatra and which describes freedom from the bondages of karma.
Hansavatar: By incarnating in the form of a swan, the Lord answered the questions of the Sankadi sages.
Nar-Narayan: From the womb of Dharma's wife Murti Devi, Nar-Narayan were born, who went to Badrivan and performed severe penance.
Kapil Muni: From the womb of Mother Devahuti, God was incarnated in the form of Kapil Muni who preached Sankhya Shastra to his mother.
Dattatreya: Dattatreya appeared from Anasuya's womb who gave Brahmagyan to Prahlad, Alarka etc.
Yagya: Incarnated from the womb of Aakuti with the name Yagya.
Rishabhdev: God was incarnated by the name of Rishabhdev from the womb of Nabhiraja's wife Meru Devi. He explained the best path of Paramhansa.
Prithu: God incarnated in the form of King Prithu and extracted many medicines, gems and grains from the cow-like earth.
Matsya Avatar: In the Chakshushamanvantar, when the entire earth was submerged, God took the form of Matsya to protect the future Vaivaswata Manu by making the earth a boat and to kill the demon named Hayagrivasura.
Kurma Avatar: To help the gods and demons during the churning of the ocean, God incarnated in the form of a tortoise.
Dhanvantari: God took the name of Dhanvantari who took out ghat of nectar from the sea and gave it to the gods.
Mohini: The Lord incarnated in the form of Mohini to provide nectar to the gods.
Srihari Gajendramoksha Dhata: God came to save Gaj from Graha. Although it was not an incarnation because in incarnation one is born again or at least takes another form; Yet in many places it has also been considered an incarnation.
Narasimha: God incarnated as Narasimha who saved Prahlad by killing the demon Hiranyakashipu.
Vamana: God incarnated as Vaman to give the kingdom of heaven to Devraj Indra by sending the demon Bali to the underworld.
Parshuram: Incarnated as Parashurama to destroy the arrogant Kshatriya kings twenty-one times.
Vedvyas: Through Parashar ji, God incarnated in the form of Ved Vyas from the womb of Satyavati, who divided the Vedas and created many excellent books.
Hayagriva : Mother Parvati had given a boon to the demon named Hayagriva that only Hayagriva could end him. The Lord incarnated as Hayagriva to end him and killed him.
Ram: God incarnated as Ram and protected the Vipras, Dhenus, Gods and Saints from the tyranny of Ravana.
Krishna: The Lord incarnated as Krishna, the son of Vasudeva and Devaki, who possessed all the arts and killed his evil demon Kansa.
Venkateshwara: Lord Vishnu in the form of Venkateshwara incarnated at the place where Bhandasura had awakened Hiranyaksha and Hiranyakashipu and on that doorstep Lord Narasimha again killed Hiranyakashipu. That place is known as Tirupati and Lord Vishnu reincarnated as Venkateswara.
Kalki: At the end of Kaliyuga, Kalki incarnation of Lord Vishnu will take place in the house of a Brahmin named Yash.