Gacha have a neutral Temperament and will only attack when provoked. The best method you can use to kill a Gacha is either with a flying creature that shoots a damaging beam/projectile, like Wyverns, or on a creature that deals significant damage and/or has high health. When attempting to kill a Gacha on foot, use of a ranged weapon is advised, Assault Rifles and Fabricated Sniper Rifles, for example, are effective so long as the distance between you and the Gacha is great enough so that they cannot reach you. If, by some circumstance, it does get to you, there are two outcomes: you die a gruesome death, or you manage to outwit it and escape.