Spectral comparison of SN 2020zbf with SLSNe-I from the literature. Left: SN 2020zbf spectra in comparison with C-rich SLSNe-I at around peak (top) and ∼30–50 days after peak (bottom). Right: comparison of SN 2020zbf spectra with typical well-studied SLSNe-I at the same epochs. The spectra are corrected for MW extinction. The spectra of SN 2020zbf, SN 2018bsz, iPTF16bad and LSQ12dlf have been smoothed using a Savitzky-Golay filter. The vertical gold dashed lines indicate the rest wavelengths of the C II emission lines.