In your Question Tags you have stated that you are using Harlowe however you haven't stated which version of that story format you are using, and answers can vary on this information. I will assume you are using Harlowe v2.1.0 which is the current default of the Twine v2.2.1 application.
You can achieve the result you want by looping the names of each of the character that the Player can have a relationship with and comparing which one has the highest score, and in the case where multiple characters have the highest score the first character will be selected.
You can use the (datanames:) macro to obtain an Array containing the names of each of the characters, the (for:) macro to loop each of them, and the (if:) macro to compare the score of the current character to that of the highest one.
A story variable named $appealedTo is used to store the name of character with highest score. It starts out with the name of the first character that is checked (because obviously they will initially have the highest score so far), and changed each time a character is found with a higher score.
{
(set: $Player to
(dm:
"Raoul", 10,
"Svi", 10,
"Stellar", 10,
"Argon", 10,
"Jiya", 10,
"Thalli", 10,
"Stron", 10,
"Arcene", 10,
"Sal", 10,
)
)
(set: $appealedTo to "")
(for: each _name, ...(datanames: $Player))[
(if: $appealedTo is "")[
(set: $appealedTo to _name)
]
(else-if: $Player's (_name) > $Player's ($appealedTo))[
(set: $appealedTo to _name)
]
]
}
$appealedTo found the Player the most appealing.
note:you can rename the $appealedTo story variable to whatever makes sense in your project, as long as you change all occurrences of that name in the above code.