The Lowest HP possible is 1, by Shedinja. Diglett has the second lowest HP which has the lvl 100 minimum of 130. Chansey and Happiny tie for lowest Attack stat, the lowest at Lvl. 100 is 13. Magikarp, Shuckle, and Blissey come in second with a minimum 22 Attack stat. Happiny and Chansey have the lowest Defense Stat at minimum 13 and Blissey is #2 at 22 Defense. Shuckle, Feebas, and Bonsly have the lowest S.Attack stats the minimum being 22. Magikarp, Happiny, and Darumaka come in 2nd with 31 as the minimum. Caterpie, Weedle, Magikarp, Igglybuff, Carvanha, and Deoxys(A) share the lowest S.Def at 40 minimum. Whismur comes in 2nd with the unique base 23 S.Defense stat which at lvl. 100 has the minimum of 45. Shuckle, and Munchlax have the lowest Speed at the minimum of 13. Trapinch, Bonsly, and Ferroseed have the 2nd lowest at 22 minimum. Although only some of them can lower their own stats, other Pokemon can lower them instead. I hope I helped :D.
P.S. all the minimum stats are at Lvl. 100