Per OP's request, here is a full solution with logical steps (except the very end, because it's too trivial to bother writing out). "Steps" uppercase-"S" are broken semi-arbitrarily at when all of a letter had been placed. Pictures are clickable to show a less-compressed version.
I use the standard coordinate system. B/R/C indicators are uppercased and letters to be placed in the grid are lowercased. “HS” means “hidden single”, “LB” means “last blank”, and “NS” means “naked single”.
Step 1:
Place all "l"s: R2 HS in R2C2, B2 HS in R1C4, R5 HS in R5C6, B6 HS in R6C7, B7 HS in R8C3.

Step 2:
Place all "b"s: R3 HS in R3C2, C7 HS in R4C7, B5 HS in R6C4, B8 HS in R8C5, B9 HS in R9C8.

Step 2.5:
Finishing off R5 in preparation for Step 3: "r" HS in R5C2 (B2 has its "r" in C5), "t" HS in R5C8, "p" LB in R5C5.

Step 3:
Place all "p"s: B1 HS in R1C2, B8 HS in R8C6, B9 HS in R7C8, B6 HS in R4C9, B4: HS in R6C3.

Step 4:
Place all "t"s: B3 HS in R3C9, B4 HS in R4C2, B9 HS in R7C7, B7 HS in R8C1, B8 HS in R9C4.

Step 4.5:
Finish B6 and place an "r" to prepare for Step 5: B6's "c" HS in R6C8 (B5 has its "c" in R4), B6's "e" LB in R4C8, B7's "r" HS in R9C3.

Step 5:
Place all "e"s: C3 HS in R3C3, C9 HS in R2C9, B2 HS in R1C5, B8 HS in R9C6, R7 HS in R7C1, C2 HS in R6C2.

Step 6:
Place all "a"s: C8 NS in R1C8 (B3's "r" must be in C7), B1 HS in R2C1, B8 HS in R8C4, B9 HS in R9C9, C3 LB in R4C3, B5 HS in R6C6, R3 HS in R3C5.

Step 7:
Place all "c"s: B1 LB in R1C1, R3 HS in R3C4, C7 HS in R2C7, B5 HS in R4C5, R9 LB in R9C2, C9 LB in R8C9.

Solution:
Place all "o"s and "r"s with trivial hidden singles.

As previous answers have pointed out, the historical figure along the diagonal is
"CLEOPATRA" and the bonus is "PLATO" (R5C5-9)