Between the 2005 and 2009 seasons, the Kansas City Royals lost the most games by a team, with 483 losses.

Interpreted as:

most regular-season losses by a team from 2005 to 2009

	TEAM	L	W	L%	G	W%	AB	R	H	2B	3B	HR	RBI	BB	HBP	SO	SB	CS	PA	TB	XBH	SH	SF	IBB	GIDP	AVG	OBP	SLG	OPS
1	Royals	483	327	.596	810	.404	27,766	3,541	7,346	1,503	196	616	3,338	2,175	308	5,213	363	178	30,671	11,089	2,315	209	213	140	699	.265	.323	.399	.722
2	Pirates	478	331	.591	809	.409	27,745	3,466	7,188	1,503	141	706	3,323	2,366	337	5,608	356	134	30,988	11,091	2,350	304	236	202	648	.259	.322	.400	.722
3	Nationals	466	343	.576	809	.424	27,425	3,409	7,011	1,482	149	677	3,249	2,760	334	5,677	391	213	31,090	10,822	2,308	358	213	219	677	.256	.329	.395	.723
4	Orioles	464	345	.574	809	.426	27,969	3,776	7,571	1,519	126	827	3,603	2,471	255	4,722	505	185	31,077	11,823	2,472	158	224	159	671	.271	.333	.423	.756
5	Rays	435	375	.537	810	.463	27,622	3,798	7,291	1,428	182	913	3,617	2,666	286	5,873	752	260	30,968	11,822	2,523	151	243	148	568	.264	.332	.428	.760
6	Reds	433	377	.535	811	.465	27,614	3,729	7,068	1,468	99	988	3,563	2,852	290	5,862	474	174	31,315	11,698	2,555	354	205	232	582	.256	.330	.424	.753
7	Mariners	429	381	.530	810	.470	28,047	3,560	7,505	1,404	137	739	3,358	2,097	260	4,804	468	179	30,805	11,400	2,280	200	201	214	647	.268	.322	.406	.729
8	Giants	427	382	.528	809	.472	27,508	3,375	7,115	1,449	195	638	3,187	2,301	239	4,901	434	167	30,626	10,868	2,282	362	216	262	679	.259	.319	.395	.714
9	Diamondbacks	415	395	.512	810	.488	27,567	3,621	7,038	1,533	197	854	3,469	2,800	265	5,755	412	143	31,181	11,527	2,584	309	240	232	587	.255	.327	.418	.745
10	Padres	414	397	.510	811	.490	27,683	3,431	6,994	1,418	166	757	3,277	2,825	248	5,751	395	145	31,305	11,015	2,341	328	221	210	622	.253	.325	.398	.723
11	Rockies	412	399	.508	811	.492	27,750	3,964	7,442	1,528	202	828	3,762	2,922	286	5,849	497	205	31,635	11,858	2,558	456	221	227	614	.268	.342	.427	.769
12	Rangers	410	400	.506	810	.494	28,184	4,201	7,614	1,638	150	1,040	4,016	2,570	244	5,857	438	125	31,388	12,672	2,828	161	229	148	614	.270	.334	.450	.784
13	Marlins	406	403	.502	809	.498	27,702	3,807	7,347	1,553	165	878	3,608	2,641	355	6,096	462	193	31,266	11,864	2,596	349	219	258	568	.265	.335	.428	.763
14	Astros	405	404	.501	810	.499	27,475	3,506	7,111	1,403	143	811	3,362	2,510	295	5,197	486	209	30,876	11,233	2,357	382	214	216	649	.259	.325	.409	.734
15	Athletics	402	407	.497	809	.503	27,739	3,689	7,117	1,448	102	761	3,518	2,952	249	5,186	365	131	31,304	11,052	2,311	123	241	118	716	.257	.331	.398	.729
16	Brewers	401	409	.495	810	.505	27,480	3,792	7,113	1,543	148	966	3,637	2,694	371	5,966	422	178	31,069	11,850	2,657	296	228	251	607	.259	.331	.431	.762
17	Braves	399	411	.493	810	.507	27,901	3,916	7,498	1,564	143	861	3,753	2,814	240	5,489	324	150	31,545	11,931	2,568	372	218	257	699	.269	.338	.428	.766
18	Blue Jays	399	411	.493	810	.507	27,912	3,849	7,474	1,641	135	835	3,679	2,602	303	4,871	347	140	31,220	11,890	2,611	142	261	138	699	.268	.334	.426	.760
19	Cubs	398	410	.493	808	.507	27,888	3,733	7,482	1,556	147	856	3,551	2,542	242	5,273	415	189	31,201	11,900	2,559	331	198	213	661	.268	.333	.427	.759
20	Indians	397	413	.490	810	.510	27,943	4,049	7,525	1,646	134	913	3,885	2,791	372	5,923	350	160	31,540	12,178	2,693	183	251	195	632	.269	.341	.436	.777
21	Tigers	397	414	.490	811	.510	28,182	3,996	7,693	1,467	211	931	3,818	2,400	259	5,415	364	162	31,260	12,375	2,609	203	216	149	660	.273	.333	.439	.772
22	Dodgers	390	420	.481	810	.519	27,773	3,720	7,436	1,416	182	713	3,544	2,803	265	5,017	565	225	31,382	11,355	2,311	323	218	270	689	.268	.338	.409	.747
23	Mets	383	427	.473	810	.527	27,727	3,830	7,396	1,465	187	819	3,626	2,727	239	5,079	759	201	31,324	11,692	2,471	384	247	296	604	.267	.335	.422	.757
24	White Sox	382	429	.471	811	.529	27,643	3,837	7,245	1,335	96	1,045	3,699	2,543	314	5,245	488	243	30,927	11,907	2,476	200	227	151	674	.262	.329	.431	.760
25	Twins	379	433	.467	812	.533	27,937	3,853	7,620	1,386	191	678	3,630	2,601	238	4,689	502	190	31,257	11,422	2,255	210	271	230	756	.273	.337	.409	.746