Bit of a strange requirement but something like this report should do the trick:
REPORT ytest.
DATA: gv_string TYPE syst_abcde,
gv_len TYPE i,
gv_ind TYPE i.
PARAMETERS: pa_let TYPE c OBLIGATORY.
START-OF-SELECTION.
SEARCH sy-abcde for pa_let.
gv_len = sy-fdpos + 1.
gv_string = sy-abcde(gv_len).
DO strlen( gv_string ) TIMES.
DO strlen( gv_string ) TIMES.
gv_ind = sy-index - 1.
IF gv_ind < gv_len.
WRITE: gv_string+gv_ind(1).
ELSE.
WRITE: space.
ENDIF.
ENDDO.
DO ( strlen( gv_string ) - 1 ) TIMES.
gv_ind = strlen( gv_string ) - sy-index - 1.
IF gv_ind < gv_len.
WRITE: gv_string+gv_ind(1).
ELSE.
WRITE: space.
ENDIF.
ENDDO.
NEW-LINE.
gv_len = gv_len - 1.
ENDDO.