Very naïve approach.
Tcl, 100 bytes
time {puts [format %[incr i]s \ ][string repe [format %c\ [expr $i+64]] $i]} [expr [scan $c %c]-64]
set i 0;while \$i<[scan $c %c]-64 {puts [format %$i.s \ ][string repe [format %2c [expr $i+65]] [incr i]]}
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Below approahes do not have a leading space
Tcl, 107 bytes
set i 0;while \$i<[scan $c %c]-64 {puts [format %$i.s \ ][string repe [format %c [expr $i+65]]\ [incr i]]}
[Try it online!][TIO-j6r5o6wd] Tcl: http://tcl.tk/ [TIO-j6r5o6wd]: https://tio.run/##RcoxDsIwDAXQq/whnRCIAbrASXA8VMYUSyVEsRFIiLMHNub3QpY@azg8zlYg3TVg2B6eV1sUOdmRXKaCJBiE1@MO7/r4fbrc220KDMk2jgwmj2ZlRtOqfxWQvmpDstW4Z84AWZEGY/70fvoC "Tcl – Try It Online"
Tcl, 109 bytes
set i 0;time {puts [format %$i.s \ ][string repe [format %c [expr $i+65]]\ [incr i]]} [expr [scan $c %c]-64]
Tcl, 111 bytes
set i 0;time {puts [string repe \ $i][string repe [format %c [expr $i+65]]\ [incr i]]} [expr [scan $c %c]-64]