PowerShell, 45 bytes

param($a)65..$a|%{" "*$i+++"$([char]$_) "*$i}

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Takes input as a literal char, then loops up through the capitals to that point, each iteration prepending the appropriate number of spaces and then the char\space hybrid.

PowerShell, 45 42 bytes

65..$args[0]|%{" "*$i+++"$([char]$_) "*$i}

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Takes input as a literal char, then loops up through the capitals to that point, each iteration prepending the appropriate number of spaces and then the char\space hybrid.

Saved 3 bytes thanks to TessellatingHeckler.