The Witch is a Pact-making Occupation. It is the most fundamental iterations of that sort of magic-user paradigm, so let's look over the core of what sort of individual typically--iconically, you might say--takes up this Occupation.
- The supernatural patron chooses the mortal to act as its agent in the world. Even if the mortal is aware of the entity's existence and seeks it out, the mortal is still no more than a helpless s act as its agent in the mortal's wupplicant compared to it, and at best can do no more than to argue that he is the best possible agent to carry out the entity's agenda. So, at best it is Employer-Employee and usually it is Principle-Agent or Master-Slave because the Witch is utterly and totally dependent upon the entity for his ability to act effectively at all.
- The supernatural patron preys upon the weak and vulnerable. You should think of the Witch's patron as a cult leader, so you're looking at the psychology of a malevolent psychopath--for a supernatural entity, definitely a primary psychopath (i.e. a born one, not someone damaged into it- that's a secondary psychopath)--who seeks to transform other individuals into vessels through which it satisfies its needs and accomplishes its goals. It seeks to do this because it is either unable or unwilling (often both) to do for itself, so it finds those who are most vulnerable to its influence- someone who is emotionally and mentally weak, often materially poor and socially incompetent or excluded and bitter about it.
- The mortal who accepts the pact offer is a loser. The Witch is usually uneducated, originally poor in financial and material terms, ambitious and prideful far beyond his actual competency and potential, outside or on the edge of social acceptability, and is unwilling (usually) or unable (rarely) to do what it takes to achieve its goals under their own power. (This is one of the reasons for why the stereotypical Witch of Hollywood and the Early Modern witch craze was a woman.) He believes that the power offered to it by the patron will be his alone to command, comes at a trivial or easily paid cost with no undesired effects or consequences, and through this power all of his grievances and troubles will be readily resolved in his favor- and his life thereafter will be that of a god amongst men (i.e. Easy Street). He is an individual of poor character, weak mind, low cunning, and powered more by desperation and delusion than anything else; if he does not develop any charisma, he will soon double-down on his bitterness and wield his borrowed power for ends far below what that power's potential actually allows. This is wholly acceptable, even desirable, on the part of the patron; Witches are wholly and utterly expendable.
Witches, therefore, are predators but not at the apex of their specific dominance hierarchy; their patron is always (at the least) above them and will deal with them when they find it necessary to do so (if not immediately with a Witch steps out of line). They're not that different from Palladium's vampires, really; the patron uses the first Witch to build up a cult, and then spins off cell-like subsidiaries through additional Witches recruited into the cult (assuming that the first Witch doesn't fuck things up), building up until they can take over or bring through the patron into the world (which usually means taking over). (This justifies the Alignment restriction.) This is an inherently predatory pattern of behavior, which cannot be and is not justifiable as being good.
Notes on Their Powers
While Witches are treated as spell-casters, Witches explicitly are utterly ignorant of how their powers work, and their mechanics would be enhanced by having their powers work differently. I recommend that the Game Master pick the Witch's powers instead of the player, and the player be told only the necessary information required: what it is, its general effect, and how often they can use it (in terms of actions/round or how often until they have to rest). In other words, more like how Palladium handles other forms of power instead of magic (which best resembles traditional High Ceremonial magic), because this is a better way to experience the Witch's relationship to the powers that he gets from his patron. (If it serves to further discourage Witches as player-characters, I find this acceptable; in my experience, most who go for this do so to troll the group and be a colossal dick.)