Klingons,Romulans.

Klingons, Romulans, Talosians, ?The Borg? (the Planet Killer was supposedly a weapon built to destroy the Borg - non-canon source), Tribbles.

The Borg didn't appear until The Next Generation and the Planet Killer was just a rogue doomsday weapon from a war where both sides had been destroyed (nothing to do with the borg)

But these did appear

The Gorn, Tholians, Mudd, Kahn (then again in Star Trek 2),

Evil Kirk (Enemy Within) Trelane (a Q type entity).

No, or it depends...

In the original series, Christopher Pike was severely injured in an accident, was a paraplegic confined to a wheelchair, and could only communicate "yes" or "no" by blinking a light with his mind. After Mr. Spock successfully took him to Talos IV (see original series episodes The Menagerie, Parts 1 and 2), the Talosians agreed to let him live out his days under their mind powers so that he would have the illusion of a young, strong body again. Eventually, of course, he would die. So depending on how long you hypothesize he could live, and what part of the Star Trek history you're talking about, the answer could be yes, no, or maybe.

In the 2009 film, Christopher Pike, in his new incarnation, did not die; he handed command of the Enterprise over to James Kirk near the end of the film.