Helvellyn is very “all up followed by all down” if you just go up Keppel Cove and back. FWIW I’d say Borrowdale Bash is a more entertaining day out, especially if you tag an extra bit on beforehand to go up the old railway line from Keswick to Threlkeld then flanks of Blencathra/flanks of Skiddaw/descent of Latrigg back down to Keswick:
…however, you won’t get this on the Borrowdale Bash: