The person who finally passed an exam after 20 years of trying is inherently stupid.
ご質問ありがとうございます。
残念ながら質問の文ではconverselyを使えないです。
The person who finally passed an exam after 20 years of trying is inherently stupid.
Inherently/「本質的に」を使います。
Converselyを使った例文は以下のような文があります。
The school has spent a great deal of money on renovating classrooms, conversely they do not have enough incase something else breaks.
ご参考になりましたら幸いです。