Acts that were to be punished by death in the Old Testament:
enticing others to serve false gods: Deut. 13:6-10
sacrificing to a false god: Ex. 22:20
offering children in sacrifice to an idol: Lev. 20:2
blasphemy: Lev. 24:16
sorcery: Lev. 20:27; Ex. 22:18
false prophecy and turning people away from God: Deut. 13:5; Deut. 18:20
breaking the Sabbath: Ex. 31:14-15; Ex. 35:2
murder: Ex. 21:12; Lev. 24:17; Lev. 24:21; Num. 35:16; Num. 35:17; Num. 35:18; Num. 35:21; Num. 35:31
striking one’s father or mother: Ex. 21:15
kidnapping a person or selling him into slavery: Ex. 21:16; Deut. 24:7
failing to keep watch over a goring animal that has killed someone: Ex. 21:29
rape: Deut. 22:25
adultery (both who committed the fornication are put to death): Lev. 20:10; Lev. 20:11; Lev. 20:12; Deut. 22:22; Deut. 22:25
carnal relations between relatives: Lev. 20:11-21
fornication of a priest’s daughter — the daughter is burned: Lev. 21:9
sodomy: Lev. 20:13; Lev. 20:15; Lev. 20:16
bestiality: Ex. 22:19
disobedience to the priests and judges: Deut. 17:8-12
an ordinary person (not a priest) entering the Tabernacle: Num. 3:10; Num. 3:38; Num. 18:7
an outsider daring to perform priestly service: Num. 3:10
an ordinary person (not a Levite) carrying the Tabernacle: Num. 1:51
going up the mountain (crossing the boundary): Ex. 19:12
In addition:
The command to kill the Midianite children and women who seduced the Israelites into the service of the idol of Peor: Num. 31:15-17
The command to kill the people of Amalek: men, women, children, nursing infants: 1 Sam. 15:3