Is a tiger more vicious than a human?

No; humans are the undisputed record holders in this field. Tigers (like other predators) will only kill for food, not for fun. In general, they will also only kill what they recognize as food - usually wearing little horns and walking on four legs - and ignore or even shrink back from anyone and anything else. And they kill quickly and outright; putting or even torturing another living being to death because it doesn't like its attitude or behaviour is typically human, not tiger behaviour.