So you need a Doctor Who villain? Here's a handy-dandy chart! Roll once for a monster-of-the-week, twice for a tense two-parter, and three times for an arch-villain! Add one or two more each subsequent appearance!
1: Has time travel powers that don't get used much.
2: Has godlike powers that don't get used much.
3: Can travel via extremely unusual means (over televisions, through minds, etc), but doesn't use it much
4: Is a large group (5-50)
5: Is a horde (uncountable quantities)
6: Is physically monstrous (insectoid, usually)
7: Is physically implacable (robotic, usually)
8: Is not solid
9: Is actually the fever dream of (or enabled by) a relatively ordinary person
10: Challenged the time lords once upon a time
11: Owns large numbers of planets somewhere
12: Is heavily armed (and threatening people, probably)
13: Is integrated into the landscape/space station/etc
14: Has weird magical powers, or technology that is effectively magic, but doesn't really understand it very well.
15: Has built another villain (roll again for their subordinate)
16: Spawns more of itself, usually via harming or crippling innocent people
17: Eats something impossible, such as time, faces, emotions
18: Is only a villain because something went haywire. Roll again.
19: Has no emotions, roll again for another power
20: The king or president or whatever of the planet.
For example, the Daleks are 19, 7, 10, and random others depending on the episode. The weeping angels are 18, 1, 4, and later are upgraded with assorted others such as 3, 17, 10, and so on.