打垮 is a resultative verb compound: 打 ('hit/attack') plus 垮 ('collapse/fall apart'). It means to defeat or destroy someone or something so thoroughly that they collapse. You can use it in military contexts (打垮敌军), business competition (打垮对手), or even figuratively (打垮某人的信心). It often appears in the 把 construction (把对手打垮) or the 被 passive (被彻底打垮).