Dajjal is blind of one eye and there is written between his eyes the word" Kafir". He then spelled the word as k. f. r., which every Muslim would be able to read. (Using translation from Muslim 2933c)
قَالَ رَسُولُ اللهِ ﷺ وَذَكَرَ الدَّجَّالَ «مَكْتُوبٌ بَيْنَ عَيْنَيْهِ كَافِرٌ يَقْرَؤُهُ كُلُّ مُسْلِمٍ»