No, the third line is not quite right.
It's more like "You're no match for me." Because in the previous two lines, he was like "I let you win/get a hit in the first time/inning", "so you should be grateful" [because you wouldn't have done it otherwise].
Does that make sense?
(1)
First, I need to make a correction on/addition to my previous post.
I wrote:
最初に一本プレゼントしてやったんを忘れたんか!!
Have you forgotten that we I had let you hit (or we I had given out a hit ) in the beginning (+of the game)?!
Change to:
Have you forgotten that I had let you have a hit (and score) first?
Reason for the change: If both teams scored ZERO for a while, then the opponent had a hit, then 最初に should be translated as my correction. It can be the first inning (初回) but it does not have to be. My original translation was based on cmertb's statement: (I think he's referring to the fact that they scored off him in the beginning of the game.)
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(2)
English is my second language, so let me just clarify a couple of things first before I comment on your post.
Your interpretations are:
1st line: "I let you win/get a hit in the first time/inning"
2nd line: "so you should be grateful"
3rd line: I am better than you.
Does "You're no match for me." mean "I am better than you", not "You are better than me?"
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(3)
The main character/speaker/the pitcher who is batting says the 1-2-3 lines.
My guess was that the opponent started to pitch one or a couple of hard balls for him(the main character) to hit, then he said the following.
<These are not translations but my interpretations.>
1st line: You (the pitcher from the other team) are pitching like you have forgotten that I let you (or you guys) have a hit first.
2nd line: Since I let you hit and score earlier, return me a favor and let me hit now.
3rd line: You can rephrase かなわんでホンマ to: マジでやってられんわ**。Seriously, give me a break.
** Since I am a Japanese native from Kansai, I did not use any translation tools or dictionaries to rephrase the sentence for your reference.