Increase the bending distance of a ``to`` path in TikZ

You can play with the looseness=<value> key: the bigger the number, the wider the curve gets. This example illustrates it, just replace the draw by this:

Replacement:

\foreach \x [evaluate=\x as \c using \x*30] in {0.2,0.4,...,3}
{\draw[->,red!\c!blue] (J) to[out=30-20*\x,in=20*\x-30,looseness=\x] (B);}

Effect:

with increasing looseness (from 0.2 to 3) the color fades from blue to red.

just tell him to move to the right by adding an intermediate point

j'ai rajouté la librairie : calc

et modifié le chemin: \draw [->] (J) to [out=0,in=-90] ($(I)+(1,0)$) to [out=90, in=0 ] (B);

\documentclass[11pt]{article} 
\pagestyle{empty}  
\usepackage{tikz}
\usetikzlibrary{arrows,positioning,automata,calc}

\begin{document}
\centering
\begin{tikzpicture}[>=stealth',shorten >=1pt,node distance=2cm,on grid,initial/.style    ={}]
    \node[state]        (0)                     {};
    \node[state]        (A) [below =of 0]       {};
    \node[state]        (B) [below =of A]       {B};
    \node[state]        (C) [below left =of B]      {};
    \node[state]        (D) [below left =of C]      {};
    \node[state]        (E) [below right =of C]     {};
    \node[state]        (F) [below left =of D]      {};
    \node[state]        (G) [below right =of D]     {};
    \node[state]        (H) [below right =of E]     {};
    \node[state]        (I) [right =of H]       {I};
    \node[state]        (J) [yshift=-2cm,below right =of G]     {J};
    \node[state]        (X) [yshift=-1cm,below =of J]       {};

    \tikzset{mystyle/.style={->}} 
    \path   (0) edge    [mystyle]   node    {}  (A);
    \path   (A) edge    [mystyle]   node    {}  (B);
    \path   (B) edge    [mystyle]   node    {}  (C);
    \path   (C) edge    [mystyle]   node    {}  (D);
    \path   (C) edge    [mystyle]   node    {}  (E);
    \path   (D) edge    [mystyle]   node    {}  (F);
    \path   (D) edge    [mystyle]   node    {}  (G);
    \path   (E) edge    [mystyle]   node    {}  (H);
    \path   (B) edge    [mystyle]   node    {}  (I);
    \path   (F) edge    [mystyle]   node    {}  (J);
    \path   (G) edge    [mystyle]   node    {}  (J);
    \path   (H) edge    [mystyle]   node    {}  (J);
    \path   (I) edge    [mystyle]   node    {}  (J);
    \path   (J) edge    [mystyle]   node    {}  (X);

    \tikzset{mystyle/.style={->,relative=false,in=0,out=0}}
    \draw [->] (J) to [out=0,in=-90] ($(I)+(1,0)$) to [out=90, in=0 ] (B);
    %\path  (J) edge    [mystyle]   node    {}  (B); %similar problem
\end{tikzpicture}

\end{document}