I honestly don't know. TDDDDI gave her some character development by making her aware of her anger issues, but later episodes such as TDA special or first TDWT Aftermath show that she still hasn't conquered her problem yet. But if she did, I can easily see her being amazing Jo-like player.
Eva's the biggest threat ever. I mean, she destroyed a camera that was already on film in Celebrity Manhunt TDA's Reunion Special. How rude. Didn't I ever tell you that camera insurance is very expensive.
Threat as a contestant? Not really. Alejandro and Heather and a lot of others are far better.
Threat as a dangerous person. Sure. Biggest? Again, not really. There were several contestants who tried to KILL someone on the show, which is far worse than destroying a camera. Most notable example is probably Scarlett.
I assume you mean she's the strongest person on the show.