Troll your friend! Every time they delete a message, the bot will repost their message in the channel.

app.js

const { Client } = require('discord.js');

const client = new Client({ disableEveryone: true });

const yourFriend = '158063324699951104'; // User ID for the friend you want to troll

client.on('ready', () => console.log(`Logged in as ${client.user.tag} (${client.user.id}) in ${client.guilds.size} server(s).`));

client.on('message', async message => {

  	// This is here because I want to ignore any messages being sent. Only want to focus on the "messageDelete" event
	if (message.author.bot) return;
	if (message.member) return;
});

client.on('messageDelete', async message => {

	if (!message.guild) return;
	if (message.author.id !== yourFriend) return;

	let msg = await message;

	message.channel.send(`${message.author} deleted: **${msg.content}**`);
});

client.login('no u');