Upper (lower) panels: Fraction f_fate of WR–NSs (WR–BHs) producing a BCO (darkest shades), a bound but not merging BCO (intermediate shades), or resulting in binary ionization (lightest shades). The remaining fraction of WR–NSs (WR–BHs) merges after a collision or a CE episode (not plotted). Each set of panels shows the same fraction f_fate for all the metallicities (columns), α_CE (rows), and combinations of CCSN and natal kick models (horizontal entries; see Table 1).