All three terms -- witch, wizard and warlock -- are applied to practitioners of magic and can be used interchangeably, but warlock has the most overwhelmingly negative connotations. Pop culture abounds with positive portrayals of female witches, like the Owens sisters (three PAIRS of sisters, actually) of Practical Magic, one of whom uses her extensive knowledge of plants to manufacture fancy personal care products. Dorothy could crush someone to death and still be asked "Are you a good witch or a bad witch?" Of course there are bad witches, but a witch could just as easily be some good-hearted person (as a witch can be either male or female) who unintentionally takes out an evil-doer or makes a mean herbal face scrub. Wizard literally means "wise man." You can be a financial wizard or a pizza wizard or a burrito wizard or a lasagna wizard...sorry, dinner just came out of the oven. As a slang term, wizard means excellent. It is sometimes used as a term for a male witch, but overall a wizard seems like a good person to be, someone who probably doesn't have Satan on speed dial.
A warlock, however? Uh...probably. It is a very old word, stretching back to the Middle Ages, and aside from being another term for a male witch, which (aagggghhh) isn't necessarily a bad thing, it can't seem to catch a break. In its earliest senses, it meant a traitor or a scoundrel, and it's all downhill from there -- a damned soul, a demon, ACTUALLY THE DEVIL, a savage, dangerous creature that probably likes to eat people and then pick its teeth with their bones, a sorcerer who colludes with and draws their powers from Satan, Satan, demons, Hell, demons, Satan, Satan, Satan. Do not buy their bath bombs. Do not eat their lasagna. Don't even bother checking their cell phone history because you're better off not knowing what kind of texts Satan sends at three in the morning.
You'd think that, given all that...Satan stuff...a warlock would be a more fitting Halloween archetype, but I guess, here in the United States at least, we have the Salem witch trials, the victims of which were largely female, to thank for cementing the image of the female witch in the public consciousness.