Some attempted sequels to The Time Machine present time-travelling Morlocks but the Morlocks belong just where Wells leaves them, creeping through the dark and confounded when the Time Traveller strikes a match.
Poul Anderson presents several much more appropriate time-travelling villains:
misguided individual fanatics, like Stane;
Neldorians from the 205th millennium, an age of bandits;
the much more sophisticated Exaltationists.
Neldorians are thugs. Exaltationists are Nietzchean egoists. I have just realized that they make an excellent contrast. The Time Patrol series exhausts the idea of time criminals, then goes beyond them - the ultimate threat being temporal chaos.