We had a small old site that wasn't worth resurrecting so we decided to have some fun and see how little it would take to kill its remaining Google rankings.
We grabbed a bunch of the spammiest expired domains and repurposed some dead domains from previous experiments. Then we pointed all of them to this old site (some 301 redirects & some run of site spammy links). We autogenerated thousands of pages to suffocate googlebot with spammy content filled with poison links. Googlebot loves crawling that infinite source of spam!
It's been over 10 weeks and that small old site is still holding steady despite exponentially boosting its backlink profile with spammy stuff.
Of course this is an isolated case and there are many moving parts so we can never fully unlock Google's secret formula but the more data & experiences we gain the better chance we have to understand things.