Medium Combat Achievement - Legiones
Currently the Medium combat achievements are all based in the mid 80s except for the 2 Legiones requirements which need 95 slayer which is a huge outlier and outside the 'mid-game' tier of bosses.
My suggestion would be to exchange the Legiones requirement with the two Arch glacor requirements in the hard tier:
Snowproblem - Defeat Arch Glacor with all mechanics enabled
Snowfall III - Defeat 25 Arch Glacor in Hardmode
Rational - Both can be completed in 'mid-game' setups with difficulty on par of the other bosses in that range. Snowproblem is the normal-mode unlock, and the 25 hardmode kills can all be done at 0 mechanic, which is a minor step up from the normal mode.
An alternative to this would be to reduce the slayer level needed for Legiones, to be more in line with the progression path of the weapon tier - 90 slayer. This would make the achievement still the one that requires the most experience from those medium combat tasks, but would bring the levels closer in line with the other tasks in the medium lists.