  This study delves into [W60] B90, one of the most luminous and extreme Red
Supergiants (RSGs) in the Large Magellanic Cloud (LMC), aiming to search for
evidence of episodic mass loss. Our discovery of a bar-like nebular structure
at 1 pc, reminiscent of the bar around Betelgeuse, raised the question of
whether [W60] B90 also has a bow shock. We collected and analyzed proper motion
data from Gaia, as well as new multi-epoch spectroscopic and imaging data, and
archival time-series photometry in the optical and mid-infrared. We found [W60]
B90 to be a walkaway star, with a supersonic peculiar velocity in the direction
of the bar. We detected shocked emission between the bar and the star, based on
the [S II]/H$\alpha$ > 0.4 criterion, providing strong evidence for a bow
shock. The 30-year optical light curve revealed semi-regular variability,
showing three similar dimming events with $\Delta V \sim 1$ mag, a recurrence
of $\sim$12 yr, and a rise time of 400 d. We found the mid-IR light curve to
vary by 0.51 mag and 0.37 mag in the WISE1 and WISE2 bands, respectively, and
by 0.42 mag and 0.25 mag during the last dimming event. During this event,
optical spectroscopy revealed spectral variability (M3I to M4I), a correlation
between the $T_{\rm eff}$ and the brightness, increased extinction, and, after
the minimum, spectral features incompatible with the models. We also found a
difference of >300 K between the $T_{\rm eff}$ measured from the TiO bands in
the optical and the atomic lines from our $J$-band spectroscopy. We inferred
that [W60] B90 is a more massive analog of Betelgeuse in the LMC and the first
extragalactic single RSG with a suspected bow shock. Its high luminosity
$\log(L/L_{\odot})=5.32$ dex, mass-loss rate, and mid-IR variability compared
to other RSGs in the LMC, indicate that it is in an unstable evolutionary state
undergoing episodes of mass loss.
