Advisor manipulated/threatened me into sharing my first authorship
These are your options:

Focus on your new project in a new lab working with better colleagues.
Do the revisions yourself.
Let the former advisor do whatever they want.


I agreed to give X co-first authorship under the condition that major revisions will be done to address all ...

You agreed to the co-first authorship.  You should not break that agreement.  Unfortunately, revisions being &quot;done&quot; is subjective so you cannot punish the other party for breaking their part of the agreement.  Next time, only agree to someone's authorship after they have earned it.