Sforno on Genesis 49:8/ספורנו על בראשית מ״ט:ח׳

1יהודה אתה, “you are the one who is fit to fill the position of royalty. The reason is that you are not stained with fatal flaws which would disqualify you from becoming king.

2יודוך אחיך, your brothers will accept you as king as they admit that you are fit to rule.

3ידך בעורף אויביך, so that they will flee from you so that you do not destroy them. We find a similar construction in Exodus 23,27 ונתתי את כל אויביך אליך עורף, “I will make all your enemies turn their backs on you.”

4וישתחוו לך בני אביך; you will rule over all your brothers (fellow tribes), but not over all the other nations,