The Bad Guy (Nemesis malum) is a top predator in its ecosystem. This species is known not only for fiercely defending its territory from potential rivals, but also for commonly encroaching on the territories of other species. Bad Guys typically assert their dominance over their territory by leaving marks of their presence, such as burning landmarks and the mangled bodies of intruding species.

Confronted with a potential rival, the Bad Guy will commonly begin an elaborate threat display to scare them off. An important part of this threat display is an intimidating musical piece playing out of nowhere. This music serves as a warning of the Bad Guy's presence to other species, signaling them to leave this territory immediately.

The Bad Guy is typically a solitary predator, but their strength often attracts a horde of symbiotes of many species, which are in general referred to as "minions". These smaller, weaker animals hunt as a pack, typically gradually wearing down the Bad Guy's prey and rivals. In return, they are allowed to share the territory of the Bad Guy in relative safety and to pick clean the scraps of the alpha predator's kills.

Despite their superior strength, Bad Guys are not always uncontested and undefeated. Other species will defend their territory from Bad Guys and sometimes even successfully repel or kill them. Such species include the Blue sonic hedgehog (Erinaceus sonicus_), the Two-tailed fox (Vulpes ducaudalis_), and the Hard-knuckled echidna (Tachyglossus pugnus).

Due to its tendency to kill or evict native animals from their territories, the Bad Guy is considered an invasive species.