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We present an analysis of ground-based and JWST observations of SN 2022pul, apeculiar "03fg-like" (or "super-Chandrasekhar") Type Ia supernova (SN Ia), inthe nebular phase at 338 d post explosion. Our combined spectrum continuouslycovers 0.4-14 $\mu$m and includes the first mid-infrared spectrum of an03fg-like SN Ia. Compared to normal SN Ia 2021aefx, SN 2022pul exhibits a lowermean ionization state, asymmetric emission-line profiles, stronger emissionfrom the intermediate-mass elements (IMEs) argon and calcium, weaker emissionfrom iron-group elements (IGEs), and the first unambiguous detection of neon ina SN Ia. Strong, broad, centrally peaked [Ne II] at 12.81 $\mu$m was previouslypredicted as a hallmark of "violent merger'' SN Ia models, where dynamicalinteraction between two sub-$M_{\text{Ch}}$ white dwarfs (WDs) causesdisruption of the lower mass WD and detonation of the other. The violent mergerscenario was already a leading hypothesis for 03fg-like SNe Ia; in SN 2022pulit can explain the large-scale ejecta asymmetries seen between the IMEs andIGEs and the central location of narrow oxygen and broad neon. We modify extantmodels to add clumping of the central ejecta to better reproduce the opticaliron emission, and add mass in the innermost region ($< 2000$ km s$^{-1}$) toaccount for the observed narrow [O I] $\lambda\lambda6300$, 6364 emission. Aviolent WD-WD merger explains many of the observations of SN 2022pul, and ourresults favor this model interpretation for the subclass of 03fg-like SN Ia.

Ground-based and JWST Observations of SN 2022pul: II. Evidence from Nebular Spectroscopy for a Violent Merger in a Peculiar Type-Ia Supernova