Negotiator Counter

A good rebel fleet of Han's Falcon, Biggs, Bistan in front with Ghost, Phantom, Cassian in reserve can easily handle a Negotiator. But does require a significant investment in the front line pilots. And generally most of them are not much use elsewhere.

Now as shown in the link provided by Antario, Geos can beat Negotiator. I believe this has also been done using Chimera. I recall a thread on this before. But whatever route you take it is not just about the fleet mix. It is about the crew gear and technique.

The only fleet outside of Malevolence or a Negotiator mirror that stands a good chance would be your Ackbar, judging by the fact you haven’t invested much in ships.

https://www.youtube.com/results?search_query=swgoh+negotiator+counter

Malevolence, Sun Fac, Vulture, Hyena; reinforced with Geo Spy, Geo Soldier + whatever (does not really matter). If you do not have Malevolence, recommend you get it.

Malevolence should be you best bet, Negotiator next, kindy tricky the mirror matches, or Ackbar (with a lot of effort)

Chimera and Executrix could do the trick with geos and maybe some cleanse of Gar Saxon / Plo Koon to pull away those dazes

Really people, start investing on ships please, by saying there's 2 fleets in defense, I assume you're on Div 2 or 1, you should be able to counter them!
I know you may not like them, but they're part of GAC, and if you want some juicy W's, you will need to invest on them

I'm 20k GP away from Div 2 and alredy have 4 viable fleets, and 2 leftover fleets (finalizer and resistance)
I always get to Kyber league, and mostly I can assure you 80% of my wins are because the enemy couldn't beat my fleet lol