Relentless Undead is a mod that focuses on making zombies harder. This isn't a traditionally AI change but rather mechanic focused. Zombies will climb each other to reach your height and ignore heights entirely to pour off high places to reach you.
Explore, loot and shoot your way through cities overrun by the infected in this zombie apocalypse modpack. Master the tech tree, craft better and stronger equipment, and eventually brave the radioactive Wasteland to find the cure.