I'm a 8th gen city gangrel w/ 2 obfuscate, 2 fortitude, 3 celerity, and 2 protean, with 5 str/4 dex/3 stamina.
Since the Tzimisces discipline tends to be animalism/fortitude/vicissitude, I'm assuming he has that with MAYBE potence/celerity since he's an elder.
If he has vicissitude 6, which gives him acid blood, I'll lose just by virtue of killing him means I also die. Horrid form is also the biggest physical stat boost in the game(+3 all physical stats).
I'll assume he has lethal damage +1 in horrid form, +3 all physical stats, maybe acid blood, and let's say 4 fortitude.
So he let's say he's at 9/8/8 for physical stats in horrid form with 4 fortitude and he also has 2 potence and 2 celerity.
Since I have obfuscate, I'd probably get at least one sneak attack in before he noticed me. So I'd bloodbuff to 9 str and 6 dex and turn on protean claws pre-ambush, then attack him from the rear while burning blood for celerity
Pre-initiative rolls, I'd roll 9d10 with most likely 5 successes. +4 additional dice for damage and +2 due to a flanking attack
Then I'd roll 9+1+6 = 16 dice for damage with most likely 8 successes for aggravated damage.
He'd probably succeed in 2/4 fortitude rolls to soak, taking 6 levels of aggravated and putting him at -5 dice.
Or I'd just use willpower to hit more or bloodbuff both str/dex to 9 pre-fight
If he has acid blood, I'll die too after I murder him since it's a difficulty 9 to dodge his blood. I'd need 6 9s just to not take 18 levels of aggravated damage.
If he ambushes me, I lose 200% since I can't get bloodbuff or a pre-initative roll hit