Comparison between the bolometric luminosity at peak of GRB-SNe, SLSNe, the RRGTs (Arcavi et al. 2016) and other luminous SNe (see Sect. 4.1.4 for more details). SN 2011kl is more luminous than any GRB-SN known and is comparable to the least luminous SLSNe (being possibly even more luminous than a few) and the RRGTs. While most of the GRB-SNe have bolometric luminosities that include a NIR correction (Olivares et al. 2012, 2015), this is not the case for all SLSNe or the RRGTs. Therefore, in some cases, the bolometric luminosities may be underestimated. Furthermore, SN 2008D, a Type Ib SN, is not associated with relativistic ejecta (Soderberg et al. 2008; Malesani et al. 2009) and therefore strictly not a GRB-SN, but a possible transition object.