An attack on someone's character or personality rather than their argument — a personal attack (ad hominem).
討論で根拠を示さずに相手の経歴を持ち出すのは人格攻撃だ。
Bringing up someone's background without evidence in a debate is a personal attack.
ネット上では匿名を利用した人格攻撃が問題になっている。
On the internet, personal attacks using anonymous accounts have become a problem.
建設的な批判と人格攻撃は違うので注意が必要だ。
Constructive criticism is different from a personal attack, so caution is needed.