So have you raised the issues with the landlord? If the landlord is non-responsive then go directly to the real estate agent.
Are you taking photos and otherwise documenting all of the breaches of by-laws? Have you issued notices to comply to the landlord?
Given the issues have been going on for 10 years
A long-term tenant (10 years) has always been troublesome
the question will be asked: “why haven’t you dealt with it until now?”
It seems that matters are escalating and will need to be addressed with strict compliance to by-laws and immediate action when further breaches inevitably occur.
Another thing, is that you’ll need to enforce the same standards for all residents, no letting anybody get away with anything. Set a high standard of behaviour and enforce it. It will be hard at the beginning but well worth it for a harmonious place to live.
Finally, is there any chance of getting a non-resident owner onto the committee? Highlight the importance of maintaining the value of their investment and providing an alternative point of view to the resident owners.
At the very least they’ll be exposed to the ‘issues’ that misbehaving tenants can cause.