  We construct a class of bottom-up holographic models with physics comparable
to the one expected from QCD in the Veneziano limit of large N_f and N_c with
fixed x = N_f/N_c. The models capture the holographic dynamics of the dilaton
(dual to the YM coupling) and a tachyon (dual to the chiral condensate), and
are parametrized by the real parameter x, which can take values within the
range 0 <= x < 11/2. We analyze the saddle point solutions, and draw the phase
diagram at zero temperature and density. The backreaction of flavor on the glue
is fully included. We find the conformal window for x >= x_c, and the QCD-like
phase with chiral symmetry breaking at x < x_c, where the critical value x_c
lies close to four. We also find Miransky scaling as x -> x_c as well as
Efimov-like saddle points. By calculating the holographic beta-functions, we
demonstrate the "walking" behavior of the coupling in the region near and below
x_c.
