I will keep it to Chicago area players which in my mind includes NW indiana. Defining killed it on a national stage is subjective. I'll stick with P4. I am taking the bait. Alexis Pupillo Al, CLS - .400 15HR's, 1.288 OPS. Congrats to her on a great season. This is second offensively to Katie Stewart, TX, LWE - .448, 1.606OPS and 24HR's. 40% of her hits are HR's(Silly)
There are many others.
Sage Mardjetko Tenn, Lemont HS- .96 ERA(Silly) 150K's in 109.1 IP
Jori Heard SC, Huntley HS - 1.95ERA
Lyndsey Grein, LWC, OR- 2.47ERA 194K's in 159IP
Brooke Klosowicz Penn St, Johnsburg HS - .341 15HR's
Breanna Hanik Penn St, Marist HS- .368 12HR's
Michela Baranbente Penn St, Lake Park- .301 8 HR's
Eileen Donahue Ill, Marist .299 - 15HR
Emily Bojan WIS, Marist - .354 - 6HR's
Hanna Conger WIS, Warren - .307
Emma Kavanaugh AZ, Barrington - .290 6HR's 1.028 OPS in only 69AB's.
Gabbi Comia FL, Hanover Central In - .337 163AB only 11k's and 9 SB's
Easton Lotus, Louisville, Marist - .356, 13-18 SB's
Sydney Doloszycki Mich St, Lake Central - .302Avg.

I am sure I am missing some. P4, Hitting .300, ERA's under 4.00, OPS over 1.00, double digit HR's all with qualifying AB's and innings pitched qualifies as killing it. I'll mention a few others who did well but not quite as well

Belle Dimitrijevic LWC, FSU 64K's in 68IP.
Caroline O' Brien , Marist, ND .288 51 GP, .926F%
Avery Houlihan Joliet West, ND -.267 53 GP ..918F%

Playing D1 softball is hard. Congrats to all of these girls for killing it.