I don't have anything for this season, but Aaron Nesmith and Andrew Nembhard were tied for the highest plus/minus in a loss in 2024-25, at +27 on March 15.

Interpreted as:

highest +/- in a regular-season loss by a player this season

	NAME	+/-	L	DATE	TM		OPP	MIN	PTS	REB	AST	STL	BLK	FGM	FGA	FG%	3PM	3PA	3P%	FTM	FTA	FT%	TS%	OREB	DREB	TOV	PF
1	Aaron Nesmith A. Nesmith	+27	1	3/15/2025	IND	@	MIL	36	30	4	2	1	0	11	16	68.8	6	7	85.7	2	2	100.0	88.9	2	2	0	3
2	Andrew Nembhard A. Nembhard	+27	1	3/15/2025	IND	@	MIL	32	7	3	2	1	1	3	7	42.9	1	2	50.0	0	0		50.0	0	3	2	3
3	Kel'el Ware K. Ware	+26	1	12/21/2024	MIA	@	ORL	14	8	7	0	0	2	4	4	100.0	0	0		0	0		100.0	2	5	0	1
4	Rob Dillingham R. Dillingham	+26	1	11/26/2024	MIN	vs	HOU	24	12	5	7	0	0	5	13	38.5	2	5	40.0	0	0		46.2	1	4	3	1
5	Yves Missi Y. Missi	+26	1	11/25/2024	NOP	@	IND	31	16	13	0	2	2	7	11	63.6	0	0		2	6	33.3	58.7	4	9	0	3
6	Oscar Tshiebwe O. Tshiebwe	+25	1	3/2/2025	UTA	vs	NOP	20	16	13	1	1	0	8	9	88.9	0	0		0	0		88.9	4	9	0	1
7	Mike Conley M. Conley	+24	1	3/17/2025	MIN	vs	IND	32	9	3	5	2	0	2	3	66.7	2	2	100.0	3	4	75.0	94.5	0	3	1	3
8	Jamal Cain J. Cain	+23	1	3/9/2025	NOP	vs	MEM	11	3	1	0	0	0	1	3	33.3	1	2	50.0	0	0		50.0	0	1	0	1
9	Isaiah Collier I. Collier	+23	1	3/9/2025	UTA	@	PHI	30	13	5	10	2	0	4	10	40.0	0	1	0.0	5	5	100.0	53.3	1	4	7	4
10	Duncan Robinson D. Robinson	+23	1	3/7/2025	MIA	vs	MIN	28	15	4	1	2	0	5	9	55.6	4	7	57.1	1	2	50.0	75.9	0	4	1	1
11	Max Christie M. Christie	+23	1	2/10/2025	DAL	vs	SAC	35	15	4	3	2	1	5	10	50.0	3	7	42.9	2	2	100.0	68.9	0	4	2	1
12	DaQuan Jeffries D. Jeffries	+23	1	2/5/2025	CHA	vs	MIL	29	9	6	2	1	0	3	7	42.9	2	4	50.0	1	1	100.0	60.5	2	4	1	1
13	T.J. McConnell	+23	1	11/18/2024	IND	@	TOR	27	10	3	7	5	0	4	11	36.4	0	1	0.0	2	2	100.0	42.1	0	3	0	2
14	Ivica Zubac I. Zubac	+22	1	3/4/2025	LAC	@	PHX	37	35	10	3	1	1	15	19	78.9	0	0		5	6	83.3	80.9	1	9	0	4
15	Al Horford A. Horford	+22	1	12/25/2024	BOS	vs	PHI	33	17	4	2	0	1	6	13	46.2	5	10	50.0	0	0		65.4	0	4	0	3
16	Jonathan Isaac J. Isaac	+21	1	4/13/2025	ORL	@	ATL	19	12	10	2	1	3	5	9	55.6	0	2	0.0	2	2	100.0	60.7	4	6	1	0
17	Jamal Shead J. Shead	+21	1	3/16/2025	TOR	@	POR	25	10	2	6	1	0	3	5	60.0	3	5	60.0	1	2	50.0	85.0	0	2	0	3
18	Dennis Schröder D. Schröder	+21	1	3/15/2025	DET	vs	OKC	27	17	3	11	1	0	6	12	50.0	4	8	50.0	1	2	50.0	66.0	0	3	0	2
19	Goga Bitadze G. Bitadze	+21	1	1/27/2025	ORL	@	MIA	22	10	9	2	0	1	4	4	100.0	0	0		2	4	50.0	86.8	1	8	0	1
20	Tristan da Silva T. da Silva	+21	1	1/27/2025	ORL	@	MIA	34	17	6	5	0	1	6	13	46.2	5	8	62.5	0	0		65.4	4	2	2	1
21	Dru Smith D. Smith	+21	1	12/16/2024	MIA	@	DET	31	7	0	2	6	0	2	4	50.0	1	2	50.0	2	2	100.0	71.7	0	0	1	6
22	Isaac Okoro I. Okoro	+20	1	4/6/2025	CLE	vs	SAC	18	7	2	1	2	0	3	3	100.0	1	1	100.0	0	0		116.7	2	0	1	1
23	Day'Ron Sharpe D. Sharpe	+20	1	2/26/2025	BKN	vs	OKC	31	25	15	5	2	3	8	10	80.0	2	3	66.7	7	7	100.0	95.6	7	8	2	4
24	Cody Williams C. Williams	+20	1	2/24/2025	UTA	vs	POR	27	8	8	5	1	0	4	9	44.4	0	1	0.0	0	0		44.4	2	6	0	2
25	Jaylen Clark J. Clark	+20	1	2/23/2025	MIN	vs	OKC	18	14	1	0	4	0	6	7	85.7	2	2	100.0	0	0		100.0	1	0	0	2