In Poland setting marked traps on your own, fenced property is illegal and their owner is responsible for any harm they cause, because there exist legal reasons to enter another person's property - for example to fight spreading fire.

However my favourite example is the law that allows any bee keeper to enter any private property if they are pursuing fleeing bee swarm.

Leaving a bear trap goes way beyond negligence, it's literally setting a trap. Similar with unmarked dangerous chemicals, they're required to be marked for good reason.

In Greece if a burglar dies while in your house you can be held responsible, even more so if you have set up traps.

If a judge or an expert is sure that you intended this outcome, and that someone is brave (or dead) enough to admit their own crime.

It's also illegal to set a trap in your own home in the US as well, decided when a property owner, tired of people breaking into his property while he was away, set up a shotgun booby trap that injured a burglar. https://youtu.be/bV9ppvY8Nx4

I wasn't sure if it is the same or similar principle in Russia or a different one that requires active care for a burglar. Unlabeled chemicals causing liability for a burglar seems extreme to me

This is an urban legend in Russia.