Here's an attempt with dynamic kerning based on the font, which eliminates some of the tweaking needed. It's not perfect and, depending on the font, a little work is needed. For pagella, scholas, termes, and a few other default fonts, the results are decent.
%\setupbodyfont[pagella]
%\setupbodyfont[scholas]
\setupbodyfont[termes]
\starttext
\newbox\MacMBox
\setbox\MacMBox\hbox{M}
\newbox\MacCBox
\setbox\MacCBox\hbox{c}
\newbox\MacKernBox
\setbox\MacKernBox\hbox{\inframed[offset=\zeropoint, width=fit]{Mc}}
\def\MacDelta{\dimexpr\wd\MacKernBox-\wd\MacMBox-\wd\MacCBox\relax}
\def\MacUWidth{\dimexpr\wd\MacCBox-.75\MacDelta\relax}
\def\MacRule{\vrule width \MacUWidth height .03em depth \zeropoint \relax}
\def\MacKern{\dimexpr\wd\MacKernBox-\wd\MacMBox-\wd\MacCBox\relax}
\def\Mac{%
M{%
\dontleavehmode{\raisebox{\dimexpr\ht\MacMBox-\ht\MacCBox}\hbox{c}}%
\kern-1.04\MacUWidth
\MacRule
\kern.08\MacUWidth
}%
}
\scale[scale=5000]{\Mac Anulty}
\Mac Anulty
\stoptext