This one goes out to all of you who can't seem to get baddies to work well with you. The main idea here is to not treat them like good-natured monsters, with the main difference between the two being what they value. Good-natured monsters live for your praise, but Bad-natured ones live for "the finer things in life" (which may just be Polish for a Durahan or Bones for a Joker). While a Bad-Natured one may certainly like you, if you get on its case it will just ignore you, and praise may be met with "Stuff the talk, just feed me, bro." In other words, Bad-Natured monsters are more expensive than Good-Natured ones, but if you know what you're doing, they can be the equal or superior of a goodie.

Unfortunately, Bad monsters are hell to raise in their early months, because their low loyalty seems to drop no matter what you do, and it seems that you can't avoid spoiling them while trying to get it up. The solution is to just feed them 4 or 5 Magic Bananas to pump up their loyalty into the 40's or 50's, at which point my method becomes alot more effective (true, this will cost a month of lifespan, but it's well worth it overall).

Once they're there, set down the ground rules quickly: If they ask for a gift right before doing a drill or some other event, give it to them, with the unstated undertone being "Okay, but you better do well." If the monster Fails or Cheats on the following task, scold them like crazy and force-feed a few Smoked Snakes, which matters to the baddie way more than your harsh words, permanently linking the idea of betrayal with that horrible taste in their mouth. After that, they're highly unlikely to ever cheat/fail after receiving a gift ever again, and once their loyalty gets up into the 80-100 range, a pre-drill gift will send their "Great" rate skyrocketing. While the frequent gifts may make them slip out of Even and into a Soft raising style, one good Smoked Snake will bring them back into line, and let them know who's boss.

On the other hand, baddies will be constantly asking for post-battle or post-drill rewards. The correct answer here is a firm "no," because they realize that you don't have to give them anything, and you never agreed to it in the first place, so only a fool would give up an uncommited-to reward like that. Their demands are more of a test to see how much they can manipulate you, and if you fail by giving in, they'll laugh with glee as their loyalty drops, because THEY'RE the master now!

Also, when a monster Cheats, go ahead and let them get away with it if you didn't bribe them before-hand, because this will keep their morality down, and the number of bribed-for Greats will easily compensate for the Cheats. Failures should be thoroughly punished for, however, or else you'll have a lazy, foul-tempered, self-centered monster before long. Finally, bad monsters (especially Jokers) can't stand to be out of the arena for long, and unless you give them a fight at least every other month, you'll have to be stuffing them full of Mint Leaves to compensate. They seem to get the most enjoyment out of either Antagonizing the enemy or outright slaughtering them, and these tactics will relieve the most stress for your bad-natured imp or brute.

In summary, a Bad-Natured monster may be better for those with big bank accounts, because of the potential to "control" their Great scores with much more dependability than a Good-Natured monster...which could be valuable to those who are sick of resetting constantly while trying to raise a monster under Dark Phoenix's method. Of course, you'll have to take out more time to use Smoked Snakes and Mint Leaves (or else take a small amount of lifespan hits by frequent fighting), and I've never gotten a bad monster with perfect 100 Loyalty...but in my opionion, the pros can outweigh the cons if you want to take that route.

Welcome to the Dark Side.

Ummm... I just Sweet Jellied my Joker to the brim.
I got it to worst just to get his attacks. He's at good now and is a HOFer. Sweet jellies I found out are good for temporary conditions for obtaining certain attacks, especially for monsters like the Jill that have techs of both natures. I got slap combo then went the other scale to get Ice meteor. They usually are better than neutral attacks of comparable stats. Of course they cost more guts though. Try to raise both extremes for a real challege.
Good in depth and somewhat too complex post, but I think praising for greats will gravitate towards good.

Excellent info on bad natured monsters, Nate. I have never really tried to raise a bad natured monster, but I did switch a Jill to bad to get bad nature techs. This is definitely one to print out and use for reference. I wanna try a bad natured Wracky soon.

Yes, praising a monster for doing Great will start to make it turn Good, but it also keeps the monster from resenting you, and encourages it to do more "Great" jobs. Plus, you can counter the morality-boosting by holding the Heel Badge.