Bizarro's personality is the same as at the end of Justice League Unlimited as well as the beginning of Superman.
Bizarro's weaknesses are unknown as following his latest upgrade, Bizarro became immune to Kryptonite.
Following the fight with Darkseid, Luthor and Slade took Bizarro and surgically switched his super breath and heat vision to give him fire breath and freeze vision. Bizarro then fought the Teen Titans. He then slammed Beast Boy into the wall and shoved Terra away. When he was contained by Raven, he was accidentally super-charged by a thing of Kryptonite Terra put in the energy. Bizarro then pushed the two aside and froze Raven, Terra, and Beast Boy. He also froze Cyborg. He then used his fire breath to cause Starfire's skirt to catch fire, and she ended up frozen by Bizarro too. He then swung Blackfire away by her hair when she attacked him and froze her too. He then froze Robin when he made to attack Slade, and he finally froze Superboy when he was about to attack Lex. Following that, Bizarro picked his teeth with the ruins of a metal bar.
When Superboy frees himself with his heat vision and frees Raven, Raven shields Superboy from Bizarro as he frees them. When Alex Lang, Luthor's son, arrives, Bizarro is told that Alex is a Teen Titan. He then fights Alex until the Titans fight back. Bizarro then pounds Beast Boy and Terra away. He's eventually convinced by Alex that Luthor is the bad guy, so he fights Luthor and is about to kill him before he's stopped by Superboy. Bizarro is then convinced by Superboy to be like Superman. When Luthor escapes and causes the building to self-destruct, Bizarro helps hold the building up as the Titans escape. Bizarro then urges Superboy and Raven to go as he fears for their lives. After that, Bizarro stats he won't die a monster. He's killed when the building collapses on him.