  Black holes in dwarf/bulgeless galaxies play a crucial role in studying the
co-evolution of galaxies and their central black holes. Identifying massive
black holes in dwarf galaxies suggests that the growth of black holes could
precede that of galaxies. However, some of the most intriguing candidate active
galactic nuclei (AGN) in small galaxies have such low luminosities that the
sample is vulnerable to contamination by other sources, such as supernova
remnants. We re-analysed Chandra X-ray Observatory observations of candidate
AGN in Henize 2-10 and NGC 4178, considering the potential signals of emission
lines in the minimally-binned X-ray spectra. We find that hot plasma models,
which are typical of supernova remnants, explain the observed spectra much
better than simple power-law models, which are appropriate for AGN. We identify
clear signals of X-ray lines in the faint X-ray source identified with the
radio source in Henize 2-10 by Reines et al. 2016. Combining our work with the
MUSE measurement of the ionization parameter in this region by Cresci et al.
2017 indicates that this radio and X-ray source is more likely a supernova
remnant than an AGN. A similar analysis of the low-count X-ray spectrum of a
candidate AGN in NGC 4178 shows that a hot plasma model is about seventeen
times more probable than a simple power-law model. Our results indicate that
investigation of X-ray spectra, even in a low-count regime, can be a crucial
tool to identify thermally-dominated supernova remnants among AGN candidates.
