I think that Krayt Dragon will slaughter both Rancors.
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Revan wasn't in his prime condition when he encountered a Krayt Dragon; the Jedi wasn't adequately prepared to handle such kind of threat on his own at that time. However, an NPC on Korriban credited Revan for surviving in an encounter with such a monster because the NPC mentioned that it was rare for anybody to survive in a confrontation with one.
Though I do believe that Krayt Dragons are too overwhelming out in the open. I am not sure if it is even possible to hurt a Krayt Dragon with a lightsaber. Furthermore enormous level of effort might be required to subdue a Krayt Dragon with the Force in direct fashion so yeah.
I wonder if Krayt Dragons ever wiped out some towns in Tatooine.