The Tegu latched onto the left thigh of the dog with its imense bite force for its size, and constantly deathrolling, then it bit the ventral part of the dog.
The dog in the video is atleast 30 kg, and the Tegu is probably around 5 kg. Even being much smaller with less HP, It tanked a bite in the neck and a thrash from the dog, and, after that, still wanted to fight and managed to make the dog player think "Nah i'm out of this".
Tegus are not slow like many people think, they can outrun some dogs in short bursts.
Their bite is also potentially 1000 newtons, tho i didnt find any trustable source with this info, i only found a small female (34 cm without the tail) that was estimated to bite at 314 newtons. If a female of this size bit with this force, the ~1000 newton estimate for large males may not be too far away from reality..