Ukraine

You may want to look at the comments from yesterdays numbers, we had some posts there about the tanks too.
A good portion of them are restored tanks from the 60's, their armor is not up to modern requirements, and they can often be taken out by relatively cheap drones.
This is why we see the weird cages Russians like to build around these old tanks, cages which most of the time do squat to protect the tank.
There are also plenty stories that even their new tanks aren't very good, they are often equipped with fake parts, like the "active" armor is merely wood pieces camouflaged to look like the real thing.

I suppose the "good" tanks are the 72's if they are restored properly, but even those are not very good, for instance they are infamous for their flying turrets, because of a failed design on how they have explosives stores.