As I put in comment, this reminded me of Shakespeare's Titus Andronicus play.
In the Wikipedia page, under the Sources section, it cites Ovid's Metamorphoses:
The primary source for the rape and mutilation of Lavinia, as well as
Titus' subsequent revenge, is Ovid's Metamorphoses (c.AD 8), which is
featured in the play itself when Lavinia uses it to help explain to
Titus and Marcus what happened to her during the attack. In the sixth
book of Metamorphoses, Ovid tells the story of the rape of Philomela,
daughter of Pandion I, King of Athens. Despite ill omens, Philomela's
sister, Procne, marries Tereus of Thrace and has a son for him, Itys.
After five years in Thrace, Procne yearns to see her sister again, so
she persuades Tereus to travel to Athens and accompany Philomela back
to Thrace. Tereus does so, but he soon begins to lust after Philomela.
When she refuses his advances, he drags her into a forest and rapes
her. He then cuts out her tongue to prevent her from telling anyone of
the incident and returns to Procne, telling her that Philomela is
dead. However, Philomela weaves a tapestry, in which she names Tereus
as her assailant, and has it sent to Procne. The sisters meet in the
forest and together plot their revenge. They kill Itys and cook his
body in a pie, which Procne then serves to Tereus. During the meal,
Philomela reveals herself, showing Itys' head to Tereus and telling
him what they have done.
So the answer may be Tereus of Thrace, son of Ares, except instead of a final battle you get birds.
From Wikipedia too:
Tereus desired his wife's sister, Philomela. He forced himself upon
her, then cut her tongue out and held her captive so she could never
tell anyone. He told his wife that her sister had died. Philomela wove
letters in a tapestry depicting Tereus's crime and sent it secretly to
Procne. In revenge, Procne killed Itys and served his flesh in a meal
to his father Tereus. When Tereus learned what she had done, he tried
to kill the sisters but all three were changed by the Olympian Gods
into birds: Tereus became a hoopoe; Procne became the nightingale
whose song is a song of mourning for the loss of her child; Philomela
became the swallow, which has no song.
And from Theoi:
TEREUS. A king in Thrake (north of Greece) whose wife and
sister-in-law slew their infant son and fed him to the king. When he
discovered their crime, they fled to escape, and sympathetic gods
transformed them into birds - nightingale and swallow. However, Ares
(most likely), sympathetic to his son, transformed the king into a
hawk, so that he could exact his vengeance for eternity on the two
For the sake of completeness, there's another mythological king that was served his own son in a banquet: Clymenus, a king of Arcadia who committed incest with his daughter Harpalyce, and as a revenge she served him up his son(s). Harpalyce was then turned into a bird.