imo it's 
because he has no special interactions with anyone and vice versa and is pretty much never spoken about in any events
even amumu has more dialogue with other champions + he is more often spoken about as well
any other opinions?
Uhmmm... 
. His whole gimmick is loneliness. Maybe he has seen less people than other champs, but in terms of emotions, he is definitely the loneliest.
Possibly 
, he was totally left at the bottom of the ocean for who knows how long.
"I miss my kind...."
You will remember Yorick Mori. Please remember Yorick Mori....
P.S. is friends with 
.
The lonliest in terms of lore? 
He's constantly being hunted down by people from his own nation of Ionia while also having to avoid all Noxians as well. "A sword's poor company for a long road."
Amumu is definitely up there though since it seems to be his thing.
I mean yeah one can also make a point about some other champs being lonely,but everyone except amumu can at least interact kinda normally with others if he/she wants to.
Guys like Aatrox are lonely because they choose to be lonely,he could interact with others if he wanted,but amumu never had that choice.
his only relationship is to Tryndamere who kind of hates him...
"Please be my friend"
" FOREVER!!!!!!"
OK
who da fk would wanna be friends with her? NOT EVEN AMUMU
Tristana has interactions with Veigar.
She basically sees him as a joke.
some other person mentioned about missing their kind.
, no other person can understand any sounds he makes.
is the only Champion Guarding Truth!
From: FuryofThornsRedo
Has lived a long life with a significant part of it walking among the ruins of his civilization,possibly regretting what happened to his brother.
Has had no interaction with anyone else , a completely isolated character.
, an abomination feared by all, his life is a neverending march of misery, all he has left is his petty hatred.
To me it's Yorick 
. His existence is an eternal heavy burden. The only things his eyes can catch are the dead bodies and friable soil. A damned creature who couldn't find love in his lore, in the player base and, most importantly, Riot Games.
Nobody has even played him
It aint easy being sadistic.
Zilean had his entire country killed
