Actually from the 15 seconds of research, it appears that NC is the only state that does not have a statute "empowering citizens to make a arrest". Security Guards are considered a citizen.
While I am not familiar with NC laws, I can only speak of my state and my experiences.
I can tell you in my 15+ years of LE, I have yet to encounter a citizen "attempting" or "making" a "citizens arrest".
I have however dealt with many theft (shoplifting) cases where a "security guard" has "detained" someone until the Police arrive.
Most states in the USA (except NC) give citizens the "legal" right to "detain" someone who has committed a FELONY, caused serious injury to another or committed a theft. A NC LEO can correct me if I am wrong (cant believe everything on the internet).
However, just because the law allows someone to "legally detain" another person, the citizen opens themselves up for "civil" issues, mainly "civil rights violations".
IMO, a citizen is only going to put themselves in a LOT of danger if they try to "detain" someone or make a "citizens arrest". I have no personal issues with "security guards" in general. Its the ones who think and act like "LEO's" that I despise!
As for "deadly force" and "reasonable force", it's simple. "Reasonable Force" is the "minimal amount of force" required to "arrest" someone or stop someone from continuing to "resist arrest" or stop a "violent act being committed", etc. and can escalate up to the use of "deadly force", which is self explanatory. Deadly Force is considered force that could cause serious bodily injury or death, examples would be hitting someone in the head with a baton, ramming another vehicle with your vehicle, or simply SHOOTING someone.
There are many other scenarios and examples of reasonable and deadly force, maybe a fellow LEO can even explain it better since I am brain dead at the moment from being awake for over 24 hours!
"TO PROTECT THE SHEEP FROM THE WOLVES, YOU HAVE TO THINK AND ACT LIKE A WOLF"