  By using the lattice Monte-Carlo simulation, we investigate the finite
temperature (T) chiral phase transition at color SU(3) gauge theories with
various species of fundamental fermions, and discuss the signal of the
(pre-)conformality at large Nf (num. of flavors.) via their comparisons. As Nf
increases, we observe stronger fermion screening effects which result from a
larger fermion multiplicity. We investigate a finite T step-scaling associated
with a uniqueness of the critical temperature (Tc) at each Nf, then the
vanishing step-scaling indicates the emergence of the conformality around Nf* =
10 - 12. Further, motivated by the functional renormalization group analyses,
we examine the Nf dependence of Tc, whose vanishing behavior indicates the
onset of conformal window around Nf* = 9 - 10.
