The massacre
He never told Izumi to go crazy and kill a lot of random people. He said he wanted him to bring strong players into the room with him. He could've gotten some fighting order of master martial artists from a temple somewhere, or professional soldiers, or find some athletes. He instead just shot up a lot of random people, and a panda bear.
Bringing of Tae into the room.
No one was holding onto Tae when they transferred back from the mission that killed her. Gantz brought her into the room on his own. He didn't have to though. Perhaps this was to keep Kurono fighting longer, in order to get the points to bring her back. Perhaps it was because after listening in on people during the mission, he realized he had made a mistake, and still has a conscious, or perhaps he simply didn't want to piss off so many of his best hunters. He knew her name, so knew about her connection to Kurono before sending them out to kill her. He didn't have to(could've just destroyed the film, or let them back after the film was destroyed), he either testing them out, or planning to bring her into the Gantz room to keep Kurono there. When Tae was resurrected, she wasn't part of the team, but actually free. Perhaps he originally planned to keep her on the team, and Kurono fighting to protect her, but saw others getting more points, and they less irritating to him than Kurono, so he let him go. Or he simply made a mistake.
Why Gantz didn't stop Kishimoto's rape.
When Kishimoto was being raped by the criminal, why didn't Gantz make the guy's head explode or something? I'm thinking he has limited awareness of what goes on in the room, he focusing on setting up the mission and making their suits. Nishi and Kurono have to poke him in the ear, whenever they want to get his attention, to show the death list, or the countdown. He seems oblivious to everything else.
Why does Gantz not give people information before the missions, to increase their chance of survival and success?
There are two possible possible reasons for this. First off, his personality shows he doesn't care about most people, considering them idiots to be tormented. If you can't figure out how to aim through a scope, and fire a gun, killing things from a safe distance, without any real danger to yourself, than you are in fact an idiot, and why would he care about you? He could also be set up to explain things only if there is a new group there, but not bother if at least one person who was there before is around, trusting them to tell the next group what they needed to know.
Why does Gantz not seem to care?
When Nishi had him show the death list, it showed more than a hundred hunters(I actually counted and posted it somewhere), which had died before they started. Gantz couldn't be getting attached to people, and was pissed off because so many people just whined constantly, and died.
Perhaps he is bond by a set of rules on what to do.
He does clearly enjoy insulting people, and being an ass, showing his personality. He isn't just a machine, but an actual person, with emotions. He is nice enough to people who accomplish missions, he insulting those who don't get any points though.
