1. Taking aggravated damage while in torpor.
If your character is reduced to
Incapacitated via lethal damage, and she takes a further
level of aggravated damage, she meets Final Death
Vampire The Masquerade 20th Anniversary p. 285
2. Losing last level of health to aggravated damage.
Worst of all, a vampire who loses his last health level due to
aggravated damage meets Final Death
Vampire The Masquerade 20th Anniversary p. 285
That would actually include seemingly differing reasons, such as exposure to sunlight, fire or being diablerised.
3. Massive physical trauma (tremendous lethal damage)
An incapacitated or torpid vampire may also be sent
to Final Death through massive amounts of bashing
or lethal trauma (decapitated, trapped under a 10-ton
rock, fed into a wood chipper, caught at ground zero
of an explosion, crushed by deep-sea pressure, etc.)
Vampire The Masquerade 20th Anniversary p. 284
Most of them kill a vampire even if it isn't incapactitated or torpid.
4. Heart removal
••••• The Heart of Darkness
A Kindred with mastery of Serpentis
may pull her heart from her body.
Vampire The Masquerade 20th Anniversary p. 210
It is implied that a vampire without access to this discipline would have a bad time removing his heart. It would make sense to assume ripping the heart out makes him go torpid, but I remember a Level 3 thaumaturgy ritual (Shaft of Belated Quiescence, page 237) that enchanted a wooden stake so that it splinters and grows into the heart as it is staked. The description claimed that un-staking is possible with multi-hour surgery, but attempting to remove it by force cause Final Death.
