Giancarlo Stanton has the most career home runs per at-bat in the postseason with 100+ at-bats, with 0.12.

Interpreted as:

most hr/ab by a player postseason, min 100 ab

	NAME	HR/AB	AB	HR	G	R	H	2B	3B	RBI	BB	HBP	SO	SB	CS	PA	TB	XBH	SH	SF	IBB	GIDP	AVG	OBP	SLG	OPS
1	Giancarlo Stanton G. Stanton	0.12	151	18	41	25	40	6	0	40	17	0	43	2	0	172	100	24	0	4	1	4	.265	.331	.662	.994
2	Babe Ruth B. Ruth	0.12	129	15	41	37	42	5	2	33	33	2	30	4	3	167	96	22	2		2	3	.326	.470	.744	1.214
3	Randy Arozarena R. Arozarena	0.1	113	11	33	23	38	5	1	17	13	2	33	3	2	128	78	17	0	0	2	2	.336	.414	.690	1.104
4	Nelson Cruz N. Cruz	0.1	187	18	50	35	52	12	0	38	19	1	45	1	1	207	118	30	0	0	2	5	.278	.348	.631	.979
5	Kyle Schwarber K. Schwarber	0.09	228	21	69	42	54	6	0	34	44	4	71	5	0	278	123	27	0	2	5	4	.237	.367	.539	.906
6	Lenny Dykstra L. Dykstra	0.09	112	10	32	27	36	6	1	19	20	2	23	5	0	136	74	17	2	0	3	0	.321	.433	.661	1.094
7	Bryce Harper B. Harper	0.09	193	17	53	41	54	13	1	34	35	2	53	8	1	232	120	31	1	1	4	5	.280	.394	.622	1.016
8	Lou Gehrig L. Gehrig	0.08	119	10	34	30	43	8	3	35	26	2	17	0	1	150	87	21	1		2	1	.361	.483	.731	1.214
9	Duke Snider D. Snider	0.08	133	11	36	21	38	8	0	26	13	1	33	1	0	149	79	19	1	1	4	2	.286	.351	.594	.945
10	Frank Robinson F. Robinson	0.08	126	10	35	25	30	5	1	19	20	3	32	0	0	149	67	16	0	0	2	1	.238	.356	.532	.887
11	Mickey Mantle M. Mantle	0.08	230	18	65	42	59	6	2	40	43	0	54	3	4	273	123	26	0	0	6	2	.257	.374	.535	.908
12	Carlos Beltran C. Beltran	0.07	215	16	65	45	66	15	1	42	37	2	33	11	0	256	131	32	1	1	2	3	.307	.412	.609	1.021
13	Jim Thome J. Thome	0.07	232	17	71	35	49	2	1	37	30	4	73	0	0	267	104	20	1	0	1	3	.211	.312	.448	.760
14	J.D. Martinez	0.07	137	10	41	16	39	5	0	34	24	1	42	0	1	164	74	15	0	2	3	2	.285	.390	.540	.930
15	Aaron Judge A. Judge	0.07	220	16	58	37	45	6	0	34	36	2	86	5	1	261	99	22	0	3	1	4	.205	.318	.450	.768
16	Delmon Young D. Young	0.07	126	9	37	14	33	4	1	22	8	2	28	1	1	137	66	14	0	1	2	4	.262	.314	.524	.838
17	Darryl Strawberry D. Strawberry	0.07	126	9	40	20	32	4	0	22	18	0	38	4	2	145	63	13	0	1	3	1	.254	.345	.500	.845
18	Manny Ramirez M. Ramirez	0.07	410	29	111	67	117	19	0	78	72	5	91	1	1	493	223	48	0	6	12	17	.285	.394	.544	.937
19	Larry Walker L. Walker	0.07	100	7	28	18	23	5	1	15	16	3	28	2	0	121	51	13	1	1	2	1	.230	.350	.510	.860
20	B.J. Upton	0.07	115	8	37	21	29	7	1	19	10	0	37	9	2	126	62	16	0	1	1	4	.252	.310	.539	.849
21	George Springer G. Springer	0.07	276	19	67	43	74	15	0	38	31	2	74	4	1	309	146	34	0	0	1	4	.268	.346	.529	.875
22	Juan Soto J. Soto	0.07	160	11	43	31	45	8	0	30	27	2	40	2	1	191	86	19	1	1	4	1	.281	.389	.538	.927
23	Jose Canseco J. Canseco	0.07	103	7	30	15	19	1	0	18	19	1	28	5	3	124	41	8	0	1	1	2	.184	.315	.398	.713
24	Jayson Werth J. Werth	0.07	227	15	63	38	57	13	2	30	41	2	76	6	0	271	119	30	0	1	4	3	.251	.369	.524	.893
25	Enrique Hernández E. Hernández	0.07	230	15	86	37	64	7	2	35	23	4	51	3	3	259	120	24	1	1	2	3	.278	.353	.522	.874