The quality of the following pictures isn't that great, but this is the biggest kill I've got a picture of to date.
It happened a bit far away and was so unexpected that I didn't have my camera setup correctly for this, but you can still see it pretty clear at least.
Mamiaua Sustainable Development Reserve in the Amazon Rain Forest, Brasil
Oct 2009

First, the catch... The big Caiman comes in fast from the right at the smaller caiman.

The smaller Caiman tries to bite back, but it's about half the size. The big Caiman is almost 12 feet or so.

Then the big caiman picks its prey entirely out of water to bash it against the ground. This looks like 2 dinosaurs fighting to me.

I think this is the coolest shot of it all.

Here the big one smashes the little one on the ground to kill it.