  We propose a minimal model that can explain the electroweak scale, neutrino
masses, Dark Matter (DM), and successful inflation all at once based on the
multicritical-point principle (MPP). The model has two singlet scalar fields
that realize an analogue of the Coleman-Weinberg mechanism, in addition to the
Standard Model with heavy Majorana right-handed neutrinos. By assuming a $Z_2 $
symmetry, one of the scalars becomes a DM candidate whose property is almost
the same as the minimal Higgs-portal scalar DM. In this model, the MPP can
naturally realize a saddle point in the Higgs potential at high energy scales.
By the renormalization-group analysis, we study the critical Higgs inflation
with non-minimal coupling $\xi |H|^2 R$ that utilizes the saddle point of the
Higgs potential. We find that it is possible to realize successful inflation
even for $\xi=25$ and that the heaviest right-handed neutrino is predicted to
have a mass around $10^{14}$ GeV to meet the current cosmological observations.
Such a small value of $\xi$ can be realized by the Higgs-portal coupling
$\lambda_{SH}\simeq 0.32$ and the vacuum expectation value of the additional
neutral scalar $\langle\phi\rangle\simeq 2.7$ TeV, which correspond to the dark
matter mass 2.0 TeV, its spin-independent cross section $1.8\times10^{-9}$ pb,
and the mass of additional neutral scalar 190 GeV.
