I think messing up with "vs0" partition will trigger a "semi-brick" which can be recovered using the "safe mode" to re-install the FW.
However, the real danger is to mess up with "os0" (which contains "low level" boot intrastructure and safe mode) or "sa0" (which contains fonts used by safe mode menu).
So if you which to brick you PS Vita, you can use VitaRW to be able to write on any partition then delete everything on "os0" using VitaShell. Disclamer: I am not responsable for any damage on your PS Vita.
Unfortunatly, like
@Tom Bombadildo said, there were some brickers which execute some bricking code (and it's not more than 20 lines of code). This is why, if you don't want to have any trouble, Henkaku settings must be configure to execute only "safe hombrews" and you should use "SafeDump" on every homebrew/backup you don't trust to flag the "eboot.bin" with "non-kernel access".
Ultimatly, there is also a mistake which must never been made: after installing a FW, never uninstall Enso if it was not re-installed. This is why there is a warning about Enso v1.0 here:
https://github.com/henkaku/enso/releases