This could be reason to serve an N5 notice to end the tenancy early. If notice is served for this reason, and the issues in the notice are corrected by the tenant, then the tenant can stay, if not, then the landlord may apply for an eviction hearing at the Landlord and Tenant Board, and try to prove their case for eviction.
For damages and clean-up costs, you would need to first get written estimates from reputable companies or contractors. Proper 24 hours’ written notice to enter must be given in order to enter to do a maintenance inspection, or if you are doing work in the unit.
You can find the notice to terminate for damages and instructions on the Landlord and Tenant Board website, here – http://www.sjto.gov.on.ca/ltb/forms/
You can also find a very good overview of how this procedure works in the Town Hall section of our website, here: http://landlordselfhelp.com/media/2016/01/TownHall_N5_public.pdf