Not cruel, because cruelty requires the causing of pain or suffering to be a willful act. If you do something that causes pain despite your intentions (e.g. sut

Not cruel, because cruelty requires the causing of pain or suffering to be a willful act. If you do something that causes pain despite your intentions (e.g. suturing), or you do something with no knowledge that it causes pain or suffering (e.g. cutting into a lobster you thought was dead, but it wasn't) - then it isn't an act of cruelty. With bonsai, you really can't say where the pain or suffering is. There arguably isn't any, since many plants actually often required to be cut for health reasons (e.g. deadheading).