User blog comment:Zathronas/Speculative author, Volume 3: Pyrrha Nykos/@comment-3257939-20141126180852/@comment-3257939-20141127005818

It's not about whether they can or can't put of a fight. It's about if the fight itself is worth of being animated and has enough action. Lark hasn't shown the full capabilities of his weapon but he also hasn't shown to be worthy enough of having a fight scene. Pyrrha knocked him out in less than a minute even though he was fighting alongside his team. So if he were to fight her again, even with his semblance and weapon at full mode, he won't win and will be knocked out in a few seconds.

The other point here is if Mercury and Emerald are capable of killing students during the tournament which I've been saying can't be since Cinder herself said that she doesn't want them killing people like they did with Tukson. Maybe they have the guts to do it but that's not Cinder's plan so they have no reason to kill Pyrrha.