LeBron James has put up the most points per game by a player younger than 20 when playing 50+ games, with 21.9 per game.

Interpreted as:

highest ppg by a player under 20 years old 50 or more games

NAME	GP	PPG	MPG	RPG	APG	SPG	BPG	TPG	FGM	FGA	FG%	3PM	3PA	3P%	FTM	FTA	FT%	MIN	PTS	REB	AST	STL	BLK	TOV	PF	+/-
LeBron James	108	21.9	39.9	5.9	6.2	1.9	0.8	3.4	8.2	18.8	43.5	0.8	2.7	30.8	4.6	6.1	75.6	4,307	2,362	634	673	202	83	367	202	-11
Carmelo Anthony	82	21.0	36.5	6.1	2.8	1.2	0.5	3.0	7.6	17.9	42.6	0.8	2.6	32.2	5.0	6.4	77.7	2,995	1,725	498	227	97	41	247	225	+65
Luka Doncic	57	20.9	32.2	7.3	5.7	1.0	0.3	3.4	6.9	15.9	43.4	2.5	7.0	35.3	4.7	6.5	72.6	1,837	1,194	415	324	57	16	194	107	-16
Kevin Durant	80	20.3	34.6	4.4	2.4	1.0	0.9	2.9	7.3	17.1	43.0	0.7	2.6	28.8	4.9	5.6	87.3	2,768	1,624	348	192	78	75	232	122	-651
Anthony Edwards	72	19.3	32.1	4.7	2.9	1.1	0.5	2.2	7.0	16.8	41.7	2.4	7.2	32.9	2.9	3.8	77.6	2,314	1,392	336	211	82	36	160	129	-228
LaMelo Ball	51	15.7	28.8	5.9	6.1	1.6	0.4	2.8	5.7	13.2	43.6	1.8	5.1	35.2	2.5	3.2	75.8	1,469	803	302	313	81	18	145	136	-84
Andrew Wiggins	54	15.3	34.6	4.3	1.9	1.1	0.6	2.0	5.7	13.1	43.5	0.6	1.8	35.4	3.3	4.4	73.9	1,867	826	233	104	60	32	106	131	-280
RJ Barrett	56	14.3	30.4	5.0	2.6	1.0	0.3	2.2	5.2	13.0	40.2	1.1	3.5	32.0	2.8	4.5	61.4	1,704	803	279	143	55	17	124	122	-325
Devin Booker	78	13.9	27.9	2.5	2.6	0.6	0.3	2.1	4.9	11.6	42.4	1.3	3.8	33.7	2.8	3.4	82.7	2,176	1,087	195	204	44	20	165	233	-380
Bradley Beal	56	13.9	31.2	3.8	2.4	0.9	0.5	1.6	5.0	12.3	41.0	1.6	4.2	38.6	2.2	2.8	78.6	1,745	780	211	137	50	29	90	113	-89
Jaren Jackson Jr.	58	13.8	26.1	4.7	1.1	0.9	1.4	1.7	5.1	10.2	50.6	0.9	2.4	35.9	2.6	3.4	76.6	1,515	798	272	64	52	82	98	220	-103
Jayson Tatum	63	13.3	30.6	5.0	1.4	0.9	0.8	1.3	4.7	9.9	47.3	1.3	2.9	43.2	2.6	3.2	82.9	1,926	835	314	88	59	50	81	131	+271
Cliff Robinson	62	13.0							5.3			0.0			2.3	3.4	69.2		807
Kevin Knox II	75	12.8	28.8	4.5	1.1	0.6	0.3	1.5	4.5	12.2	37.0	1.7	4.9	34.3	2.2	3.0	71.7	2,158	963	335	82	43	24	114	175	-637
Jabari Smith Jr.	79	12.8	31.0	7.2	1.3	0.5	0.9	1.3	4.6	11.3	40.8	1.5	4.9	30.7	2.1	2.6	78.6	2,451	1,010	569	101	43	74	104	227	-555
Josh Giddey	54	12.5	31.5	7.8	6.4	0.9	0.4	3.2	5.2	12.4	41.9	1.0	3.9	26.3	1.0	1.5	70.9	1,700	674	421	345	51	20	171	88	-299
Dwight Howard	100	12.4	33.3	10.6	1.0	0.9	1.6	2.0	4.5	8.8	51.1	0.0	0.0	0.0	3.5	5.3	65.2	3,327	1,243	1,061	100	94	163	203	297	-216
D'Angelo Russell	56	12.1	27.2	3.6	3.4	1.1	0.2	2.4	4.7	11.2	41.8	1.5	4.5	34.3	1.3	1.8	70.7	1,523	678	199	189	64	9	134	93	-289
Kobe Bryant	150	11.7	21.1	2.5	1.9	0.8	0.4	1.8	3.8	8.9	42.5	0.8	2.4	35.4	3.3	4.2	80.1	3,159	1,759	374	290	123	63	269	282	+324
Luol Deng	61	11.7	27.3	5.3	2.2	0.8	0.4	1.9	4.6	10.6	43.4	0.5	1.9	26.5	2.0	2.7	74.1	1,663	711	322	135	48	27	118	98	+158
Chris Bosh	63	11.2	32.9	7.3	1.0	0.7	1.4	1.4	4.2	9.3	45.7	0.0	0.1	37.5	2.7	3.9	68.4	2,074	704	461	65	46	86	86	176	-139
Coby White	55	11.1	24.3	3.5	2.4	0.7	0.1	1.5	4.1	10.9	37.0	1.8	5.3	33.8	1.2	1.7	74.7	1,337	612	192	132	41	4	80	91	-177
Jeremy Sochan	56	11.0	26.0	5.3	2.5	0.8	0.4	1.7	4.5	9.9	45.3	0.6	2.4	24.6	1.4	2.1	69.8	1,458	614	295	142	43	23	97	138	-235
Kevin Garnett	80	10.4	28.7	6.3	1.8	1.1	1.6	1.4	4.5	9.2	49.1	0.1	0.4	28.6	1.3	1.9	70.5	2,293	835	501	145	86	131	110	189
JR Smith	76	10.3	24.5	2.0	1.9	0.7	0.1	1.4	3.9	9.8	39.4	1.1	3.7	28.8	1.5	2.1	68.9	1,859	782	152	142	55	11	109	135	-397