Riki-Oh 2: Horobi no Ko

Both OVA's feature conflict among brothers in an apocalyptic society, although the manga for Riki-Oh has better story structure. 

Riki-Oh and Hokuto no Ken are similar both thematically and stylistically. The events both happen in a post-apocalyptic world, where the main protagonist is a roaming martial arts master with a strong sense of justice and muscular physique. These two anime also share the same theme: that of brotherly conflict. 

Both anime have been influenced by Hokuto no Ken, and share some plot elements. In both anime, the protagonist is blessed with inhuman strength and uses it to defeat evildoers. Also, both anime show a conflict between two siblings. Apart from the plot, both anime also have a similar character design, having many manly muscular male characters. 

Both are based on manga by the same author: Tetsuya Saruwatari. Both anime were made in the same period (1989-1990). They have main characters who look almost identical, as well as similar animation. They both have similar plot elements, since they focus on a battle between former friends/siblings. Also, they have a lot of action scenes. 

Post-apocalyptic worlds, depraved characters, gore, violence and non-stop action. In both anime, you will find these themes. Also, both are the second entries in their respective film series. 

Both anime have a muscular martial arts master as their main character. Also, in both anime, the main character has to fight in a death tournament and must defeat his family members. 

Post-apocalyptic worlds, depraved characters, gore, violence and non-stop action. In both anime, you will find these themes. 

The events in both of these OVAs happen in a post-apocalyptic world. The main characters are both tall, muscular and very powerful men. They also try to help innocent people by killing evildoers in gory and violent ways.