A superior force will decimate an inferior one every time in a direct conflict. Which is why the inferior force reverts to going underground and fighting dirty. French Revolution in WWII, Vietcong in Vietnam, Americans in US Revolutionary War, Native Americans at Custer's Last Stand... Ewoks on Endor (lol).
Guerilla warfare .. fight dirty, hit-n-run, ambushes, traps.
Clandestine Ops .. send in spies and/or convert civilians & troops on the other side to spy for you (pay them bribes, find members that are unhappy and find ways to make their lives better, etc), infiltrate their day-to-day lives as civilians and set bombs, steal their weapons, sabotage their gear, plant false information.
Propaganda ... war isn't just physical, it's social. So, you start leveraging propaganda. You make a martyr out of every person the enemy kills. You setup social situations where you make the enemy look bad to the eyes of the people (and army is only as good as the civilian population supporting it, so if you can demoralize the populace, you may be able to push popular opinion away from war and towards peace... if the superior army is running the government (military dictatorship), then maybe enough propaganda can get the civilian population to revolt and fight for you). You send out fliers with lies of whatever truths you want people believe (if you say something often enough and loud enough, eventually someone will believe it). Treat prisoners of war respectfully and show them that you're not "the bad guys" and make them question their side of the war.. then send them back home (a seed of doubt planted can grow into a revolution).
War really comes down to tactics.. who has superior tactics. Weapons are just tools, and only useful if you know how to use them.
Sun Tzu's theory was that a superior general won based on tactics and training of troops, not necessarily how advanced the weapons were. You could have a bungling general fielding troops with power armor, laser rifles, etc.. but poor tactics has them getting slaughtered. A great tactician can win b/c they know how best to leverage the troops, tools and arenas available to them.
A good general herds the enemy around. They hit certain places to lure the enemy out to vulnerable areas where it's easier to ambush, attack or trap them.
Sun Tzu was known for running a small band of guys through a large army by constantly keeping one step ahead of them and staying light and mobile. While the enemy general had his heavily armed troops marching constantly and getting demoralized (b/c they couldn't' catch up to Sun Tzu's fast-moving strike force).. eventually Sun Tzu had lured them into an area where he could slaughter them. The heavily armed military was tired after weeks of non-stop marching with little rest. They were also demoralized from having to constantly keep moving and changing routes to keep up with Sun Tzu's seemingly sporadic attacks all over the nation. But, Sun Tzu's goal was to tire out the opponent and wear down their morale while also secretly leading them by the nose to a perfect ambush spot. When he finally fought them, his smaller force won over the superior force.
So, technology doesn't really matter...
Well... it does if the superior force decides to go to extreme lengths.
EG: every alien invasion movie ever made never thinks that if the aliens are so advanced they can fly through space to get to us, then they could probably just abduct one of us to analyze, and create an aerosol virus that would wipe out the entire world's population in a month. Sit in orbit, drop a canister in a populated area, and let viral vectors go to work as it spreads and wipes everyone out.
A superior military that has biologics and chemical weapons could get pretty nasty. They could also be ruthless.. if they have a bomb go off in a village.. they just wipe out everyone in that village hoping they get the spy.
Again, though, this goes back to tactics.. what do you have available, how can you use it, and to what lengths are you willing to go to win.
Sun Tzu feeling on "winning" was that you haven't truly won if there's nothing left. So, he wanted to win by taking over the enemy by keeping as much intact as possible.. that way civilians could rebuild infrastructure quickly and get back to their lives. Plus, you would already have a standing army ready to go... you just retrain them and get them on the same page as you (which is easy if you defeated them with superior tactics.. an army wants to follow the best military leader.. just like an individual wants to follow the strongest leader).
If the superior military doesn't care about the lesser military or population, they could just nuke them from orbit and glass the world (apply so much thermic force that the entire crust just turns to glass / ceramic). Scorched Earth.
So, it would depend on the conflict between the two groups, the morals of them (how far are they willing to go), what they want to have left to consider "victory" (decimate everyone? have people left over? have infrastructure remaining?)
A neutron bomb could wipe out all living organisms and keep infrastructure intact.
So... technology doesn't really matter.. it's tactics and how far people are willing to go. Lower tech societies tend to be willing to do more and go farther, b/c they are simply more desperate. But, they do reach a point...