FredeBot, unlike the other two FredeBots, was not originally created to destroy Frederwick, but was created by V.G to be his personal body guard after Deedle tricked him into losing his immortality to Deedle members. FredeBot Mark III was made to be extremely strong and protective and, V.G changed the design, so unlike the other FredeBots it could not program its own missions that cannot be beaten, and V.G had to program that, but it could still have other missions beside "protect V.G" though they can fail.
FredeBot worked as it was programmed, until one day when it damaged it memory chip, and when it went to get a new one, it found FredeBot Mark II's one, and put it in, making it have the memory of FredeBot Mark II, making it want to destroy Frederwick and the rest of the human race forever, and have the upgraded skills and technology of FredeBot Mark III, including the power to hack into any electronic device.
FredeBot Mark III then went to Deedle Headquarters to tell them he was good (though he wasn't) and they should let him join Deedle and replace Frederwick, but since Deedle had already encountered two evil FredeBots, and that plan had already been used on them by FredeBot Mark I they didn't believe him. But FredeBot, using his hacking skills, hacked into a nearby parked truck making it go shooting at Johnny Pickles, and then FredeBot saved Johnny, making it look like he was really a good guy, and letting him join Deedle.
But, of course FredeBot's real plan was to enslave humanity, so he built an entire army of FredeBot Mark IIIs so he could take down any enemy. But Frederwick, being depressed by Emily Jr's death, and feeling really bad after being replaced again, did a spell with Dark Magik to give him superpowers, which led to him getting Johnny Pickle's, and Johnny Pickles getting no powers, but it also made Frederwick become FREDERWICK BAD BOY, the evil side of Frederwick!!!!!!!
Frederwick Bad Boy (check his page for more information) then TOOK DOWN the army of FredeBots, killing every one, except for one FredeBot that survived without him knowing.
Later, and I mean a couple of weeks later, when Frederwick was reverted to his normal powerless good boy self by Johnny Pickles, FredeBot, with a new army of FredeBots attack again, but V.G just shut them all down with his controller button, because at that point everyone had had enough of the end of the world kinda stuff.