tfblade speaks with a very specific accent,
I forgot where hes from but if you listen to him speak for more than 10 minutes it's very apparent
In the clip he slurs his speech and very clearly says "kill them, you n-idiots"
He inserts the sound of an 'N' at the start of idiots but it's obviously not the N word because there is no hard 'G' or 'R' sound present, and you need your ears checked if you think you heard either one of those
He's literally being punished for having an accent
Edit: found a post explaining it better
https://www.reddit.com/r/leagueoflegends/comments/bgsvlo/update_tf_blade_twitch_ban/elntiln/
I spent too much time with this responding to someone else who is adamantly defending that Blade swore.
Here's a logical explanation of what happened:
Persian is the dominant language of Iran, his home country. In modern Persian, there is no phoneme ɪ, a near-close front unrounded vowel, the vowel that begins the English word "idiot". The closest vowel phonemes to ɪ in Persian are
e̞, a mid front unrounded vowel, and, much more loosely,
æ, a near-open front unrounded vowel. These vowel sounds commonly follow consonant sounds and don't begin words like they commonly can in English. The English word "these" ends in the phoneme z, a voiced alveolar sibilant, but he pronounces it only partially-voiced, making it sound more like s, the voiceless alveolar sibilant. If you look at this chart you can clearly see that the phonemes s, z, and n are all alveolar. Knowing that, and knowing the previous word, "these", ends in either s or z, it's easier for a non-native speaker who is quickly speaking to blend the end phoneme of one with with the beginning phoneme of the next. Since there is no ɪ in Persian, it's easier for him to use e̞, a vowel phoneme that doesn't begin words in Persian. What does he naturally do? Merge the s/z with an n phoneme to assist his pronunciation of the foreign vowel phoneme ɪ in "idiot". His accent not only excuses the sound you heard, but phonetics explain it pretty clearly.