I do expect that u win against that lvl 18 dude.
He is probably someone who just returned to the game.
In my last 2 seasons (when i was lvl 5 and 6 I played 2 times the same CL final against a guy who was lvl 13 and 14 (now 15)
Lost the first one due to stupidness from my side. Won the second 0-6 thnx to good tactics. (With some nice help from the forum)
Personally I like it better when I am up against some 100%+ player, as that I am up against some 45% dude.
If I would win every game 7+-0 I am off in 2 weeks.
But goodluck to u.