1."全世界背叛你"在中文中是行得通的,但是在英文中,最好转化成“世界的每个人背叛你”;
2.“在你身边”表达的其实就是“和你在一起”,所以我认为“be with you”比“be by your side”更简洁更好;
3.后一句的“背叛”实际上是用来与前一句呼应,但在英文中不存在这一点,所以一句话中出现两个“betray”显然不地道.
我的翻译是:
Even everyone in the world betrays you,I will be with you,not afraiding of being against the whole world.