If someone decides to go to many of my posts (answers or questions), and downvote all of them in revenge, what can I do?
StackExchange has an automated script to scan voting patterns and automatically reverse any abnormal patterns of serial voting (both downvotes and upvotes). However, this runs once every 24 hours according to this Meta SE answer.
So, the recommendation is to wait for up to 48 hours for the automatic voting correction to take place. If it does not take place, then please report to a moderator using a flag. You may flag any one of your own answers or questions that was suspected to have been revenge downvoted. One is enough.
If the abnormal pattern of voting was automatically corrected, the Reputation tab on your profile will show "Voting corrected (learn more)".
I get the impression that there are abnormal votes and just assume that someone is probably multiaccounting and that sometimes people will downvote because they don't like something trivial or do it to annoy the poster.
I don't really care about it because moderators can't see the voterid and it's difficult to show malice in voting.
Many of my answers get downvoted but as a rule someone will correct the downvote and i almost never get -2 lest i post something weird.
Seems like the votes are in general not readily dispersed and one can often guess who is doing the downvoting...
If people downvote an obviously good answer, then i will flag it and maybe make a commotion about it.
It is probably not wise to focus too much on how others give you upvotes or downvotes. Instead, it is probably better to focus on your own intention and motivation for providing questions and answers on the site. Is it a good intention? Is it a good motivation? Was that intention/motivation executed skillfully and with wisdom? If so, then it matters little what the upvotes or downvotes are.
Best to let the upvotes/downvotes simply act as a tool reminding us to continually check our own intention/motivation/skill with discriminating wisdom and act accordingly. At least that is what I sincerely try and do even if in a fumbling and unskillful way. Practice makes perfect, right? :P