No main antagonist

Should only be used if unusual, for example puzzle and sport games commonly don't have any kind of antagonists, main or secondary ones.

Since this is only excludes the existence of main antagonist, this is NOT the same as no antagonists/opponents. As such, the various -menace tags do not invalidate this tag.

Group or larger things (e.g. an organization/government) should be judged carefully. If it's a whole organization with no specific person driving the antagonism within it (the mooks do it on their own as part of their job rather than some commander type persecuting the protagonist).
For example: police forces hunting a criminal protagonist would not generally count as main antagonist (no involvement with the police chiefs or similar commanding individuals, nor are any of the police usually characterized to any notable extent). However, a protagonist fighting oppressive government (dictator) would count however, as the protagonist is far more likely to encounter and oppose the actual people controlling the organization (in this case, the dictator is the main antagonist).

Generally speaking, this includes all cases where there's no "unique" character/person or group (e.g. council) involved in the antagonism.