SCDE1
SF9
STR1D2
SREDF21
FRED
STER2R4

SCDE
SF
STR1D
SREDF2
FRED
STER2R

cat user324294
SCDE1
SF9
STR1D2
SREDF21
FRED
STER2R4

sed 's/[0-9]$//' user324294
SCDE
SF
STR1D
SREDF2
FRED
STER2R

sed 's|[0-9]$| |g' file

SCDE
SF
STR1D
SREDF2
FRED
STER2R

[0-9]$

sed 's/[0-9]$//' test.txt

sed 's/[0-9]*$//' test.txt