電車の中などで見る最近の若い者の態度の悪いこと、全く不愉快極まる。
I believe 全く不愉快極まる is the predicate and the rest before the comma is the subject, but I don't understand how the two parts are connected by こと. Could you help me figure it out?
彼らは騒々しいことおびただしい, as well as the entry in meikyo 事柄の程度が最高である意を表す。「面白いことこの上にない」「手のかかることこの上にない」 and other predicates mentioned in that linked Q&A (はなはだしい) as well the answer itself all point to the predicate being something which indicates high degree or frequency.
But 全く不愉快極まる is not specifying degree or frequency, it’s saying it’s very 不愉快
Because of this I think the 全く不愉快極まる sentence seems more to me like just a normal sentence, not an occurrence of this construction.
電車の中などで見る最近の若い者の態度の悪いこと、実におぞましい。電車の中などで見る最近の若い者の態度のいいこと、この上なく心温まる。I do find myself wanting to put in emphasis words for the sentence to sound good though.