user24788: I'm looking for a tool where I can input a name (e.g. Hans Niemann, Levy Rozman, Eric Rosen etc.) and it will tell me the highest rated player they beat in chess (FIDE rated games). I appreciate any help!

user27380: If you have Chessbase:

Step one: Filter every game played by your player and the result (i.e. your player won; you can do this for White and Black separately and merge the results, but you shouldn't even need to).
Step two: Sort by rating.

That's it.

user32763: This is possible to do with scid vs pc (free and open source) as follows

Load a database (e.g., caissabase, which is free)
filter games in which player X plays white and wins
in the filtered collection in the game list window click on the button 'black elo' to sort the collection by black elo.

Do the same by filtering games in which X plays black and wins.

user4418: No such tool exists. You will have to write it yourself. Here is what you need to do:

Go to the "Individual Calculations" page for the player you are interested in. For Hans Niemann that is here.
You will see the word "available" for each month/time control combination where he has FIDE rated games. Click on one of these, for instance Standard/September 2022.
There you will see that he had two wins against Kobalia(2578) and Idani(2641). Record these as you wish.
Rpeat for all periods where results are "available" for the time control(s) you are interested in.

I would suggest you write a program to do screen/data scraping to speed this up.

24788: <p>I'm looking for a tool where I can input a name (e.g. Hans Niemann, Levy Rozman, Eric Rosen etc.) and it will tell me the highest rated player they beat in chess (FIDE rated games). I appreciate any help!</p>
 27380: <p>If you have Chessbase:</p>
<ol>
<li>Step one: <a href="https://en.chessbase.com/post/fun-and-instructive-the-new-search-mask-in-chessbase-15" rel="nofollow noreferrer">Filter</a> every game played by your player and the result (i.e. your player won; you can do this for White and Black separately and merge the results, but you shouldn't even need to).</li>
<li>Step two: Sort by rating.</li>
</ol>
<p>That's it.</p>
 32763: <p>This is possible to do with scid vs pc (free and open source) as follows</p>
<ul>
<li>Load a database (e.g., caissabase, which is free)</li>
<li>filter games in which player X plays white and wins</li>
<li>in the filtered collection in the game list window click on the button 'black elo' to sort the collection by black elo.</li>
</ul>
<p>Do the same by filtering games in which X plays black and wins.</p>
 4418: <p>No such tool exists. You will have to write it yourself. Here is what you need to do:</p>
<ol>
<li>Go to the &quot;Individual Calculations&quot; page for the player you are interested in. For Hans Niemann that is <a href="https://ratings.fide.com/profile/2093596/calculations" rel="nofollow noreferrer">here</a>.</li>
<li>You will see the word &quot;available&quot; for each month/time control combination where he has FIDE rated games. Click on one of these, for instance <a href="https://ratings.fide.com/calculations.phtml?id_number=2093596&amp;period=2022-09-01&amp;rating=0" rel="nofollow noreferrer">Standard/September 2022</a>.</li>
<li>There you will see that he had two wins against Kobalia(2578) and Idani(2641). Record these as you wish.</li>
<li>Rpeat for all periods where results are &quot;available&quot; for the time control(s) you are interested in.</li>
</ol>
<p>I would suggest you write a program to do <a href="https://en.wikipedia.org/wiki/Data_scraping" rel="nofollow noreferrer">screen/data scraping</a> to speed this up.</p>
