  We obtained near-infrared spectra of 26 SDSS quasars at $0.7<z<2.5$ with
reported rest-frame ultraviolet $M_{\rm BH} \sim 10^{10}M_{\odot}$ to
critically examine the systematic effects involved with their mass estimations.
We find that AGNs heavier than $10^{10}M_{\odot}$ often display double-peaked
H$\alpha$ emission, extremely broad FeII complex emission around MgII, and
highly blueshifted and broadened CIV emission. The weight of this evidence,
combined with previous studies, cautions against the use of $M_{\rm BH}$ values
based on any emission line with a width over 8000 km/s. Also, the $M_{\rm BH}$
estimations are not positively biased along the presence of ionized narrow line
outflows, anisotropic radiation, or the use of line FWHM instead of $\sigma$
for our sample, and unbiased with variability, scatter in broad line equivalent
width, or obscuration for general type-1 quasars. Removing the systematically
uncertain $M_{\rm BH}$ values, $\sim10^{10}M_{\odot}$ BHs in $1\lesssim z
\lesssim 2$ AGNs can still be explained by anisotropic motion of the broad line
region from $\sim10^{9.5}M_{\odot}$ BHs, although current observations support
they are intrinsically most massive, and overmassive to the host's bulge mass.
