Line Manager pressurising me to do her dirty work

[SunshineOnARainyLeith]

Employer is in a bad financial state, and now advertising for voluntary redundancies.

Just prior to the redundancy announcement my line manager told me to find an external replacement for a colleague, to cut down on costs. It would be presented as my idea. She attempted to blackmail to do this. I checked my job description and nothing in it about this kind of task. Other more alarming signs of incompetency/lack of support from her, including when a colleague deliberately pushed me and she took no action.

I've resigned and feel better for it. But would appreciate some replies on the lines of "yes that's toxic"!

I have been there for less than 2 years so little to no redress via constructive dismissal.

I'm not sure I fully understand. If you were assaulted by a colleague and she took no action, yes that's terrible.
If she asked you to take sone action to reduce costs that you decided was not in your JD and told her that, not sure why that is so bad. What was the blackmail element? Probably more context needed.