Here's a hint in case you just want a push, try printing 'document' and poke around in it
Else just go and run the code in the spoiler below, requires 26.6GB and it needs to be a .js file
Note, only unlocks Steam achievements, doesn't affect in game counter

/** @param {NS} ns **/
export async function main(ns) {document.achievements.push("UNACHIEVABLE")}

You could also use this to unlock other achievements if you know the names, but that's no fun

This little bit of code should unlock all achievements at once, and it only uses 1.6GB

/** @param {NS} ns**/
export async function main(ns) {
eval("ns.bypass(document.achievements.push('CYBERSEC', 'NITESEC', 'THE_BLACK_HAND', 'BITRUNNERS', 'THE_COVENANT', 'DAEDALUS', 'ILLUMINATI', 'BRUTESSH.EXE', 'FTPCRACK.EXE', 'RELAYSMTP.EXE', 'HTTPWORM.EXE', 'SQLINJECT.EXE', 'FORMULAS.EXE', 'SF1.1', 'SF2.1', 'SF3.1', 'SF4.1', 'SF5.1', 'SF6.1', 'SF7.1', 'SF8.1', 'SF9.1', 'SF10.1', 'SF11.1', 'SF12.1', 'MONEY_1Q', 'MONEY_M1B', 'INSTALL_1', 'INSTALL_100', 'QUEUE_40', 'HACKING_100000', 'COMBAT_3000', 'NEUROFLUX_255', 'NS2', 'FROZE', 'RUNNING_SCRIPTS_1000', 'DRAIN_SERVER', 'MAX_RAM', 'MAX_CORES', 'SCRIPTS_30', 'KARMA_1000000', 'STOCK_1q', 'DISCOUNT', 'SCRIPT_32GB', 'FIRST_HACKNET_NODE', '30_HACKNET_NODE', 'MAX_HACKNET_NODE', 'HACKNET_NODE_10M', 'REPUTATION_10M', 'DONATION', 'TRAVEL', 'WORKOUT', 'TOR', 'HOSPITALIZED', 'GANG', 'FULL_GANG', 'GANG_TERRITORY', 'GANG_MEMBER_POWER', 'CORPORATION', 'CORPORATION_BRIBE', 'CORPORATION_PROD_1000', 'CORPORATION_EMPLOYEE_3000', 'CORPORATION_REAL_ESTATE', 'INTELLIGENCE_255', 'BLADEBURNER_DIVISION', 'BLADEBURNER_OVERCLOCK', 'BLADEBURNER_UNSPENT_100000', '4S', 'FIRST_HACKNET_SERVER', 'ALL_HACKNET_SERVER', 'MAX_HACKNET_SERVER', 'HACKNET_SERVER_1B', 'MAX_CACHE', 'SLEEVE_8', 'FAST_BN', 'INDECISIVE', 'CHALLENGE_BN1', 'CHALLENGE_BN2', 'CHALLENGE_BN3', 'CHALLENGE_BN6', 'CHALLENGE_BN7', 'CHALLENGE_BN8', 'CHALLENGE_BN9', 'CHALLENGE_BN10', 'CHALLENGE_BN12', 'CHALLENGE_BN13', 'BYPASS', 'PROTOTYPETAMPERING', 'UNCLICKABLE', 'UNDOCUMENTEDFUNCTIONCALL', 'TIMECOMPRESSION', 'REALITYALTERATION', 'N00DLES', 'EDITSAVEFILE', 'UNACHIEVABLE', 'DEVMENU', 'RAINBOW', 'TRUE_RECURSION'))")}