The Non-Aggression Principle [NAP] is the only tenant of anarchy. The NAP prohibits initiatory force, including threats of force and fraud. All members of sapient species have self-ownership and so the NAP applies to them. The NAP, and therefore anarchy, has nothing to say on any other issue. The NAP does not prohibit defensive force, retaliatory force, or proportionality as it has nothing to say about things that are not initiatory force. The NAP is not a complete moral system and it does not purport to be.
The State is an organization who’s purpose and function is to initiate force. There is nothing mystical about it; it is an organization of humans who habitually initiate force strategically and at random. At present, people comprising the State are the biggest initiators of force. For this reason the State is the main focus of many anarchists.