Difference and nuance between することはない and する必要はない/する可能性はない?

Question

I understand the grammar point "Verb (Dictionary Form) + ことはない" can mean either "There is no need" or "There is no possibility" depending on context. However, what are the differences? Are there any nuances which I should be aware of? Can they simply be interchanged in any circumstance? "There is no need" example: わざわざここに来る必要はない vs わざわざここに来ることはない "There is no possibility" example: 今日の会議を忘れる可能性はない vs 今日の会議を忘れることはない

Answer 1

It seems that this expression contains an element of encouragement or to give advice. The

わざわざここに来る必要はない - There is no need for you to come. (Statement of fact.)

わざわざここに来ることはない - Oh, there's no need for you to come all this way. (Alleviating someone's concern about having to go somewhere and do something)

今日の会議を忘れる可能性はない - There's no possibility that I'll forget today's meeting. (Statement of fact, and kind of stiff.)

今日の会議を忘れることはない - Oh, there's no way I'd forget about today's meeting! (Alleviating someone's concern that you may have forgot)

Other examples:

心配することはないよ！僕も手伝うから頑張ろう。There's no need for you to worry! I'll help you too, so let's do this!

困ったことがあったら、いつでも私に言ってね。一人で悩むことはないよ。If there's anything bothering you, please tell me. You don't have to go it alone!

そのことでは彼にも責任があるから、君だけが責任を取ることはないよ。He bears some responsibility for that too, so you can't shoulder all of the blame.