What exactly is the problem? Kill the posse, kill the beasts, eat an ambush charge or two from the trogs and slowly piecemeal away his army. Mammoth...
Kreoss can't stand Reznik, likely because Reznik doesn't have to follow any codes and is, (at the) end of the day, the most blunt Assassin ever. Thyra has to sneak in and use subterfuge to get her target, Reznik (will) just walks up and say "give me this or I kill everything."