The most helpful framework for approaching bad parts of a social system is to build similar structures for working with a bad code system. The strangle method

The most helpful framework for approaching bad parts of a social system is to build similar structures for working with a bad code system. The strangle method for dealing with a legacy code base can work for social situations. Create an overarching social structure, with help from other co-workers, where the toxic person has their own bubble of influence, make sure the structure is secure, and then slowly reduce the size of the bubble. An overarching social structure looks like normalized communication channels (one communication channel as opposed to several, scheduled meetings instead of one-offs so everyone is invited), clear lines of responsibility, and a steady escalation chain. Formal review processes in particular, as long as they don't grow too much cruft, is the easiest way forwards to start shrinking the bad-actor-bubble. Coincidentally, this idea can be used for bad purposes, and is often how programmers can get strangled (so to speak) within their own organization.