What's your threat model? Are you trying to get away with sending death threats to the executives through the survey? Because of they're not if you're commiting crimes like that.
Are you worried that telling your boss they suck at their job could lead to repercussions for you? Sit down with a friendly manager and ask to look at the report from last anonymous survey to see what lengths the company goes to in order to anonymize results. Some companies only give lip service to the idea, other companies actually do want truthful feedback. I've seen managers fired over poor feedback. I've also seen bad managers get worse after a feedback cycle.
If the "anonymization" consists of "your team rated you X on "listens to feedback", you're fine. If the feedback is divided into "teammates who have been at the company longer than X months/years", then don't consider it anonymous - it's too easy for a smart, vindictive manager to unblind the anonymization by slicing the data just the right way. If 100% of women on the team think the manager is an asshat, but there's only one woman on the team... that's not anonymous. Survey givers try to prevent that, and won't report on eg gender break downs in that case, but I wouldn't bet my career on that.
And of course, in the short answer section, you can't give personally identifiable examples of where your manager has failed you.
Ultimately though, if you're that afraid of your workplace, you might want to consider finding a job somewhere less... adversarial. You have to deal with the company a majority of the week. It behooves you for it to be somewhere you don't feel like it's a fight most days. (Unless you like that, of course.)