In terms of global average temperature, we consider "average temperature in the decades before industrialization" as "healthy/fixed" and the previous temperature plus 4-6 degrees Celsius as "broken beyond repair".

In reality it's of course a bit more complicated since earth is complicated. Another good proxy for "fixed" would be "glaciers and permafrost exist and are not decreasing" while broken would be "large areas in the third world have become uninhabitable to humans"