There is an immeasurable number of deities in Hinduism, and in Hindu lore quite a few gods come to earth to fight and destroy evil.
One of the most common deities associated with the destruction of evil is Shiva.
Among his traits is the destruction of evil and ignorance, and he is also said to protect his devotees from evil and to protect all that is good. At one time, he also appeared as a terrifying beast named Sharabha to pacify Vishnu in the form of Narasimha, after he became berserk, so that he may be calm and harmonious again.
Speaking of Shiva, his wife, Shakti, also fights against evil. Not only that, but in many forms, such as Durga and Kali. In fact, in Hinduism, Durga is very much a symbol of the triumph of good over evil, as well as feminine power. Shakti is also said to be assisted by seven mother goddesses of war and emancipation known as the Matrikas. They are Brahmani, Vaishnavi, Maheshvari, Indrani, Kaumari, Varahi, and Chamundi.
Vishnu also fights against evil, usually in the form of his avatars.
My favourite example is Varaha, the boar-headed third avatar of Vishnu who came to save the earth (or a goddess represneting earth) from an evil demon named Hiranyaksha, who stole the world and hid it in the primoridial waters. He slew Hiranyaksha and rescued the earth from the primordial waters she was hidden in, and thus the world is saved.
Other avatars were sent to fight evil, including Narasimha (who was sent to kill an evil demon who could not be killed by man or deva and so had to be killed by an animal-like entity), Rama (who defeated a evil demon king named Ravana who could not be killed by god or demon and, despite his noble and honorable character, was too arrogant and prone to evil deeds), Krishna (who was said to come to earth to destroy evil demons), and Kalki (who is said to come and destroy evil in the future, though Kalki’s presence as a bringer of the end and judge of mortals does not make sense in Hindu philosophy).
Some question the validity of the actions of some avatars. For instance, Vamana, the avatar who is a dwarf or young brahmin. He is said to come to earth to take back the three worlds from Mahabali, who supposedly stole them. But it could also be said he merely wanted to test Mahabali and remove his pride and bring him to “perfection”, which he was close to at the time he seized heaven. Then there’s Parashurama, who pretty much went around killing every member of the Kshatriya caste, guilty or innocent, and somehow gone unpunished. And often times, some of his avatars, including Kurma, Mohini, and Vamana, might just be assumed merely to win a competition with the rivals of the devas, the asuras.
Vishnu is also said to preserve righteousness in the form of Nara-Narayana, and there are depictions of Vishnu that have him holding a sword among other objects.
Other gods often worshiped to destroy evil and for protection include Ganesha, who is sometimes worshiped as a destroyer of evils, perhaps related to his role as the lord and destroyer of obstacles, Hanuman, who is a courageous god believed to be a destroyer of evil spirits and is often worshiped as a protector, and Murugan (a.k.a. Kartikeya) who is seen as a destroyer of evil and protector of good.
Hindu gods also appear in Buddhism, especially in Japanese Buddhism, often as deities who destroy and/or protect from evil as well as protecting the home, protecting from illness, and protecting the Buddhist teachings.
To be fair plenty of deities in Hinduism (as well as Buddhism) have symbolism pertaining to war, combat, destroying evil, and protecting the innocent or good, or at least there are many depictions, variations, or forms of said gods.
Perhaps themes here include, besides the triumph of good over evil, strength and driving out fear (since aggression drives out fear).
Perhaps these deities come to the world to punish and destroy those who roll the dice too many times, those who are so evil that truly they deserve to be wiped from the earth, those who threaten the world with their excess and their malice, those who oppress, and those who corrupt themselves and the world. In a way, in fighting evil, they encompass justice, war, power, and balance if you consider that much evil happens when one stops thinking about the need to control yourself by applying balance and thought to ones actions.