Jermaine O'Neal is the youngest player off the bench in a game with 20+ points. He was 18 years and 101 days old versus the Seattle SuperSonics on January 22, 1997.

who is the youngest nba player to score 20 points in a game off the bench

Interpreted as:

Who is the youngest NBA player to score 20 or more points in a regular-season game off the bench?

NAME	AGE	PTS	DATE	TM		OPP	MIN	REB	AST	STL	BLK	TOV	FGM	FGA	FG%	3PM	3PA	3P%	FTM	FTA	FT%	PF	+/-
Jermaine O'Neal	18-101	20	1/22/1997	POR	@	SEA	25	6	0	0	2	1	8	10	80.0	0	0		4	4	100.0	4	+19
Kobe Bryant	18-133	21	1/3/1997	LAL	vs	SAC	22	5	1	2	2	0	6	10	60.0	0	2	0.0	9	10	90.0	1	+10
Kobe Bryant	18-148	21	1/18/1997	LAL	vs	DET	32	2	5	1	0	4	8	13	61.5	3	5	60.0	2	2	100.0	1	-1
Kobe Bryant	18-228	24	4/8/1997	LAL	@	GSW	25	2	3	1	0	5	9	11	81.8	2	3	66.7	4	7	57.1	3	+23
Tracy McGrady	18-265	22	2/13/1998	TOR	@	NJN	37	8	1	1	1	1	7	16	43.8	0	0		8	10	80.0	1	-9
GG Jackson II	19-027	20	1/13/2024	MEM	vs	NYK	27	6	1	0	2	2	9	14	64.3	2	4	50.0	0	0		0	+2
GG Jackson II	19-029	23	1/15/2024	MEM	vs	GSW	29	6	1	2	2	2	6	9	66.7	5	8	62.5	6	8	75.0	3	+23
CJ Miles	19-032	23	4/19/2006	UTA	vs	GSW	33	6	4	1	2	0	8	13	61.5	2	5	40.0	5	8	62.5	3	+6
Jaren Jackson Jr.	19-034	24	10/19/2018	MEM	vs	ATL	28	7	2	1	2	2	8	12	66.7	2	4	50.0	6	9	66.7	5	-8
GG Jackson II	19-053	27	2/8/2024	MEM	vs	CHI	32	9	1	1	0	0	9	18	50.0	4	9	44.4	5	6	83.3	2	-13
GG Jackson II	19-059	20	2/14/2024	MEM	vs	HOU	24	9	0	0	3	1	8	15	53.3	3	5	60.0	1	2	50.0	2	+2
GG Jackson II	19-060	27	2/15/2024	MEM	vs	MIL	30	1	0	0	1	3	10	17	58.8	6	10	60.0	1	3	33.3	3	+12
Kobe Bryant	19-069	23	10/31/1997	LAL	vs	UTA	33	3	5	1	0	1	5	13	38.5	0	2	0.0	13	14	92.9	1	+18
AJ Griffin	19-074	24	11/7/2022	ATL	vs	MIL	31	4	1	3	0	1	10	15	66.7	2	6	33.3	2	2	100.0	2	+28
Kobe Bryant	19-078	25	11/9/1997	LAL	vs	GSW	24	3	5	3	1	0	11	18	61.1	2	3	66.7	1	2	50.0	1	+14
Kobe Bryant	19-088	20	11/19/1997	LAL	vs	MIN	34	3	3	2	0	2	9	18	50.0	1	5	20.0	1	1	100.0	2	+33
Andre Drummond	19-091	22	11/9/2012	DET	@	OKC	21	8	0	1	1	1	8	10	80.0	0	0		6	9	66.7	2	0
Kobe Bryant	19-092	24	11/23/1997	LAL	vs	LAC	29	5	4	4	0	1	8	21	38.1	0	2	0.0	8	9	88.9	3	+18
Jonathan Kuminga	19-100	25	1/14/2022	GSW	@	CHI	26	3	3	1	3	0	10	12	83.3	2	4	50.0	3	4	75.0	5	+22
Kobe Bryant	19-106	21	12/7/1997	LAL	vs	CLE	29	4	2	0	0	1	5	15	33.3	2	4	50.0	9	10	90.0	5	+3
Bilal Coulibaly	19-109	20	11/12/2023	WAS	@	BKN	34	7	3	4	0	2	8	12	66.7	4	7	57.1	0	1	0.0	0	+2
Kobe Bryant	19-109	20	12/10/1997	LAL	@	GSW	30	6	4	1	0	2	7	15	46.7	2	3	66.7	4	8	50.0	0	-4
Jonathan Kuminga	19-111	22	1/25/2022	GSW	vs	DAL	18	5	0	0	0	1	8	9	88.9	4	4	100.0	2	2	100.0	0	+16
Kobe Bryant	19-111	27	12/12/1997	LAL	vs	HOU	26	5	1	2	0	1	8	15	53.3	2	4	50.0	9	10	90.0	1	+13
Kevin Knox II	19-112	26	12/1/2018	NYK	vs	MIL	37	4	4	1	1	2	9	20	45.0	5	12	41.7	3	5	60.0	3	+5