The اهْبِطَا مِنْهَا جَمِيعًا (123) mean "both of you go down together". This command can be in reference to Sayyidna 'Adam علیہ السلام and the shaitan in which case the meaning of the phrase بَعْضُكُمْ لِبَعْضٍ عَدُوٌّ (123)
some of you enemies of some is obvious, namely that the two of them will remain enemies in the world also. However if it is argued that the Shaitan had already been expelled from Paradise long before these events occurred, then it would be correct to assume that these words have been addressed to Sayyidna 'Adam علیہ السلام and Sayyidah Hawwa' ( علیہا السلام ) meaning thereby that their children would cherish hostile feelings towards one another and mutual hostility among the children embitters the lives of the parents.