Keith Courage in Alpha Zones (1988)

Now the Battle is in Your Hands. You are Keith Courage. Struck by a giant meteor, the world has been invaded by strange creatures from another planet. Burrowing deep within the Earth's surface, the Planet of B.A.D. (Beastly Alien Dudes) seeks to take over the world. As a member of N.I.C.E. (Nations of International Citizens for Earth), your mission is to defeat B.A.D. and bring peace back to the world. Armed only with a sword, you must first defeat the outpost guards. Then, enter the Underworld. Here you activate the awesome Nova Suit. A secret force left to you by your fallen father, you are half man, half mechanical monster. Nearly invincible, your sword cracks with the power of lightning, as you wreak havoc on the fearsome Dudes. Your goal is to reach the Robo Zone (the seventh Alpha Zone), headquarters of B.A.D. Succeed here and you will have won the game, recapturing the Earth and restoring humanity's place in the universe. You have help along the way. Four friends offer you advice, swords, bombs, and extra lives. Collect the stolen riches left behind by the invaders and buy your way out of trouble with money.