Kaliyo vs. Akaavi Spar. Who wins?
Personal Answer: I have to go with Kaliyo. Akaavi is a fierce warrior, but Kaliyo isn't afraid to fight dirty and will do whatever it takes to survive.
You HAVE to be kidding!
A random thug VS a respected Mandalorian clan's finest warrior who's killed Jedi. Who's first kill was a mercenary like Kaliyo, who she killed with an improvised flamethrower at the age of 8.
Unless I've missed something, Kaliyo has nothing at all in her history to show she has anywhere near the skill to kill full on Jedi, or the experience and training growing up a Mandalorian would have given her.
Akaavi's Mandalorian training started at 3 years old. Is hardened enough that when her lover's clan refused to aid her clan, she left him and vowed revenge.
Kaliyo on the other hand has no professional training. No high risk kills. Is a bad enough fighter to have been caught and arrested more than once.
Side by side there's no comparison. One was trained nearly from birth to be a top notch fighter and has killed actual Jedi to prove her ability. The other can't even keep minor criminals in check while working for a Hutt.
And as far as fighting dirty, I think an 8 year old MAKING HER OWN FLAMETHROWER IN THE MOMENT to cook someone to death counts as fighting dirty.