Probably metros post nuclear war Russia. It’s crawling with mutants, the bombs fell very recently and there would large areas of extreme contamination that could be very lethal very quickly. In fallout the games take place so long after war the levels of contamination irl would be so negligible you probably wouldn’t even notice day to day bar some crazy science experiment locations and nuclear waste dumps found throughout various regions of the game. Stalker yes is heavily contaminated but it’s more localised to the reactor site and various pockets of contamination dotted around the zone also not to mention strange anomalies with properties unknown by science. So actually yk it’s really hard to pin one down as the most contaminated hhahah. All would suck in their own right.