If the answer is invalid without the poster's knowledge, it shouldn't be deleted without notifying the poster first and giving him some time to fix histheir mistake.
Immediately flag invalid answers of type 4 as spam or rude or abusive.
If your own answer turns out to be invalid, delete it yourself.
Immediately leave a comment on all invalid answers that are not your own.
Immediately flag invalid answers of type 5 as not an answer.
If you are a trusted user, the challenge is fairly active and the answer should not get converted into a comment, consider voting to delete instead.
Give the poster time to fix or self-delete histheir invalid answer of type 1 to 3.
If a sufficient amount of time has passed (say 48 hours) or the answer was deliberately invalid, flag the answer as in need of moderator intervention, providing an explanation of why it is invalid.
If you are a trusted user and the challenge is fairly active, consider voting to delete instead.
If you fix your self-deleted answer, undelete it.
If you fix your answer and cannot undelete it yourself, flag it as in need of moderator intervention, requesting its undeletion.