MenaceMenace is an evasion ability.
A creature with menace can’t be blocked except by two or more creatures. (See rule 509, “Declare Blockers Step.”)
Multiple instances of menace on the same creature are redundant. (CR 702.111) (This creature can't be blocked except by two or more creatures.)
When this creature enters, if an opponent lost life this turn, put a +1/+1
counterTo counter a spell or ability is to cancel it: remove it from the stack without resolving it. A counter on an object or player is instead a marker that changes characteristics or interacts with rules or abilities; for example, a +1/+1 counter modifies a creature’s power and toughness. (CR 701.6; 122.1) on each other Vampire you control.
As long as an opponent lost life this turn, each other Vampire you control enters with an additional +1/+1
counterTo counter a spell or ability is to cancel it: remove it from the stack without resolving it. A counter on an object or player is instead a marker that changes characteristics or interacts with rules or abilities; for example, a +1/+1 counter modifies a creature’s power and toughness. (CR 701.6; 122.1) on it.