には agent or object of the potential form?

Question

This sentence is translated as: "In the end I could never beat him, not even once" by JTest4You

結局彼には、一度も勝てなかった

So the agent in I which is assumed here. But I was under the impression that for passive/potential verbs the agent is what attaches to に.

What is the correct grammar of には here ?

Answer 1

If a verb normally takes に in active voice, it usually retains its original role in a potential sentence.

Verbs that do not take に in active voice:

• 私には見えます。 I can see it.
• 彼には食べられます。 He can eat it.
• 君には分からない。 You cannot understand this.

Verbs that take に in active voice:

• 東京には行けます。 It's possible to go to Tokyo.
• この部屋には入れない。 You cannot enter this room.
• 彼には勝てなかった。 I could not defeat him.
• 彼女には会える。 You can meet her.
• 親には見せられない。 You cannot show this to my parents.

This is not necessarily true in passive sentences. For example, 親に見せられた is ambiguous and it means either "Someone showed it to my parents (against my will)" or "My parents showed it to me (against my will)" depending on the context.