Streets of Rage

From Wikipedia

Similar to the game Golden Axe which was released two years prior by Sega, enemies walk onto the screen from both sides as well as occasionally appearing from other locations. The player must defeat each opponent to progress through eight locations, known as rounds. With the exception of round 7, there is a boss battle at the end of every round with a disproportionately large enemy. Unlike its sequels, none of the enemies are named within the game (only in the Japanese version's manual) and only the bosses have life gauges. In Streets of Rage, the special attack is assistance from a police car which will pull up at the level's left and fire explosives, taking health from all enemies. The player is given one special attack per life or per level, with power-ups shaped like police cars giving another. In round 8, the special attack can't be used. Depending on whether the game is played as one-player or two-player co-op and the player accepts or rejects Mr. X's offer to become his henchman, there is a possibility for an alternate ending where the player becomes the new head of the crime syndicate.