I suppose you have imported a solution pack (also called 'framework) Archimate - Metamodel Customizations
This has altered the standard metamodel and you want to restore this standard metamodel.
There is no easy cancellation.
The easiest is to to restore the environment (system database). I assume you have a physical backup made before import of the solution pack
Otherwise, the only option I see is to identify the metamodel changes by analysing the file SystemDb.mgr and try to create a command file that cancels these changes.
<mega installation>\MEGA FrameWork\Archimate\Archimate - Metamodel Customizations\Files\SystemDb.mgr
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