From the iNat help page:
If you disagree with an identification, the best thing to do is to add an identification of your own. It’s helpful to provide a reason for disagreement in a comment.
For incorrect IDs, simply correct your own ID. You can always tag knowledgeable people to help outvote the “maverick” ID.
For the observation where you are no longer certain if you have the correct ID, you can always change your ID to a higher taxon. Then it will take at least one more person to confirm the ID to reach research grade. You can include a comment on the observation stating the reason for your uncertainty.
If this is a reoccurring issue with the same user on many of your observations, you can block someone. See here.
A number of threads have covered this same topic:
Issue with users automatically agreeing to an identification
Overzealous Identification