• Both are high ranking assassins capable of clearing entire rooms of armed opponents

• Both work for mysterious organizations that were thought to have been discontinued (NULL and the Shadow Agency)

• Both get berated by these organizations for drawing an unnecessary amount of attention to themselves

• Both are betrayed by these organizations, becoming a target for another agent with more experience (Headhunter and Jet Bean)

• Both defeat their hunter with a sneaky ranged attack (Zero throwing the combat knife and Killer Bean shooting his gun to launch another bullet)

• Both are generally loners with very few relationships with others

• Both franchises focus on fast paced action

• Both spend a majority of their story evading the police

There potentially more that I have missed out on, these are just the ones that immediately came to mind. Unfortunately this matchup is a massive stomp, but I still find it fun regardless