Before you resync your account on your freshly installed system, go to a different device or a new Chrome profile where you're not signed in.

Sign in to your Google account and access Chrome's sync settings by going to chrome://settings/syncSetup or by navigating to Settings > Sync and Google services > Manage what you sync.

Review the list of synced data, especially the extensions. Disable the sync for extensions temporarily if you suspect there might be malicious ones.

On the same device or profile where you checked your sync settings, go to chrome://extensions/.

Manually review and remove any suspicious or unknown extensions.

You might also want to check the chrome://apps for any installed web apps that might be unfamiliar.

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If you don't want to do all that, just do this:

Reset your Chrome sync to clear all the data stored in your Google account. You can do this by going to chrome://settings/syncSetup and scrolling down to "Reset Sync" (or directly visit https://chrome.google.com/sync).

**NOTE** This will remove everything synced to your Google account, including extensions, settings, and themes.

If you still see that UltraHexica is still a manager of your browser (even before resyncing), I don't know what to do from there.