Slith Bloodletter 

Creature — Slith
Whenever this creature deals combat damage to a player, put a +1/+1 counter on it.
{1}{B}: Regenerate this creature.
click a line to search just that ability, click more to combine them
Cards that do something similar expected a card that isn't here?
Reports become test cases the matcher is graded against before an update ships. Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math, and examples like yours decide which differences should count.
Bloodcrazed Neonate 100%
$0.13#22367
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Slith Ascendant 100%
$0.05#24600
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Heirs of Stromkirk 100%
$0.11#23476
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Slith Strider 100%
$0.10#27715
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Erdwal Ripper 100%
$0.25#25110
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Havengul Vampire 100%
$0.26#20873
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Stromkirk Patrol 100%
$0.12#27043
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Arcbound Slith 100%
$0.55#8872
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Hexgold Slith 100%
$0.18#22586
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Slith Predator 100%
$0.12#28589
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Falkenrath Exterminator 100%
$0.24#17576
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Slith Firewalker 100%
$0.14#27699
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Bloodmad Vampire 100%
$0.20#12098
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Stromkirk Noble 100%
$0.12#13270
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Guild Thief 100%
$0.21#22501
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."
Markov Blademaster 100%
$0.31#13295
"Whenever this creature deals combat damage to a player, put a +1/+1 counter on it."